A man pets his dog on a bench in Moscow, Russia, Thursday, April 23, 2015, as they both enjoy a warm spring sun. It's not very warm in Moscow for this time of the year, about 9 °C (48 F) which is 3-4 degrees less normal. (Photo by Pavel Golovkin/AP Photo)

Passengers ride a subway train decorated with World War II era posters during its first trip in Moscow, Russia, Wednesday, April 22, 2015. Russia will celebrate the 70th anniversary of the Victory in WWII on May 9, 2015. The poster at right reads, “What have you done for the front!”. (Photo by Denis Tyrin/AP Photo)

Passengers take a subway train decorated with World War II era posters during its first trip in Moscow, Russia, Wednesday, April 22, 2015. Russia will celebrate the 70th anniversary of the Victory in WWII on May 9, 2015. The poster reads, “Glory to soldier the conqueror!”. (Photo by Denis Tyrin/AP Photo)

Passengers ride a subway train decorated with a famous World War II era poster reading “Motherland calls!” in Moscow, Russia, Wednesday, April 22, 2015. Russia will celebrate the 70th anniversary of the Victory in WWII on May 9, 2015. (Photo by Denis Tyrin/AP Photo)

Boston Marathon runner Tenee Ramsdell, left, gets a hug from Evangline Gersish, both from San Diego, before boarding a shuttle bus in Boston to the starting line in Hopkinton, Mass., Monday, April 20, 2015. (Photo by Robert F. Bukaty/AP Photo)

A migrant is helped disembark in the Sicilian harbor of Pozzallo, Italy, early Monday, April 20, 2015. About 100 migrants, including 28 children, were rescued on Sunday by a merchant vessel in the Sicilian Strait while they were trying to cross. Another smuggler's boat crammed with hundreds of people overturned off Libya's coast on Saturday as rescuers approached, causing what could be the Mediterranean's deadliest known migrant tragedy and intensifying pressure on the European Union Sunday to finally meet demands for decisive action. (Photo by Alessandra Tarantino/AP Photo)

The Arab (Ala.) High School team races their rover past the space shuttle as students, teachers, and engineering enthusiasts from all over the world gathered under the space shuttle at the U.S. Space and Rocket Center for the 2015 NASA Human Exploration Rover Challenge Saturday, April 18, 2015 in Huntsville, Ala. The Rover Challenge requires student teams to design, construct, test and race human-powered rovers through an obstacle course simulating terrain potentially found on distant planets, asteroids or moons. Teams race against the clock to finish the course with the fastest times, vying for prizes in competitive divisions. (Photo by Eric Schultz/AP Photo)

Gwen Stefani, of the band No Doubt, performs at the Global Citizen 2015 Earth Day on the National Mall, Saturday, April 18, 2015, in Washington. (Photo by Nick Wass/Invision/AP Photo)

In this Friday, April 17, 2015 photo, Egyptian volunteers at a water stop offer water to runners participating in Cairo's annual Half Marathon in the Heliopolis district in Cairo, Egypt. Young Egyptians are once again organizing on social media and taking to the streets of Cairo by the hundreds every Friday, not to protest injustice or clash with police, but to enjoy long runs through one of the world's most crowded and chaotic cities. (Photo by Amr Nabil/AP Photo)

In this Friday, April 17, 2015 photo, an Egyptian volunteer rides her bicycle as she leads runners participating in Cairo's annual Half Marathon in the Heliopolis district in Cairo, Egypt, Friday, April 17, 2015. (Photo by Amr Nabil/AP Photo)

An Egyptian volunteer holds water bottles for passing runners participating in Cairo's annual Half Marathon in the Heliopolis district in Cairo, Egypt, Friday, April 17, 2015. The streets are jammed at nearly all hours with smoke-belching microbuses, manic taxis, speeding motorbikes and the occasional donkey cart. The crumbling sidewalks are often worse – and yet despite all the obstacles, young Egyptians have launched several increasingly popular running clubs over the past two years. (Photo by Amr Nabil/AP Photo)

An Israeli soldier places a small national flag with a black ribbon on the grave of a fallen soldier on the eve of Memorial Day at the Kiryat Shaul military cemetery in Tel Aviv, Israel, Tuesday, April 21, 2015. Israel marks the annual Memorial Day in remembrance of soldiers who died in the nation's conflicts, beginning at dusk Tuesday until Wednesday evening. (Photo by Ariel Schalit/AP Photo)

Women's division winner 18-year-old Nada Zimmermann of Innsbruck, Austria, prepares to hurl a banjo into a heavily polluted New York waterway during the fifth annual Brooklyn Folk Festival's Gowanus Banjo Toss, Sunday, April 19, 2015, in the Brooklyn borough of New York. Zimmermann won a new banjo for throwing the instrument a record-setting 67-feet. (Photo by Kathy Willens/AP Photo)

Women's division winner 18 year-old Nada Zimmermann of Innsbruck, Austria, hurls a banjo into a heavily polluted New York waterway during the fifth annual Brooklyn Folk Festival's Gowanus Banjo Toss, Sunday, April 19, 2015, in the Brooklyn borough of New York. (Photo by Kathy Willens/AP Photo)

Partygoers listen to music and smoke marijuana on one of several days of the annual 4/20 marijuana festival, in Denver's downtown Civic Center Park, Saturday April 18, 2015. The annual event is the second 4/20 marijuana celebration since retail marijuana stores began selling in January 2014. (Photo by Brennan Linsley/AP Photo)

Partygoers listen to music and smoke marijuana on one of several days of the annual 4/20 marijuana festival, in Denver's downtown Civic Center Park, Saturday April 18, 2015. (Photo by Brennan Linsley/AP Photo)

Partygoers listen to music and smoke marijuana on one of several days of the annual 4/20 marijuana festival, in Denver's downtown Civic Center Park, Saturday April 18, 2015. (Photo by Brennan Linsley/AP Photo)

People walk past a statue of Soviet Union founder Vladimir Lenin during celebration of his 145th birthday at the Lenin Hut Museum at Razliv lake, outside St.Petersburg, Russia, Wednesday, April 22, 2015. (Photo by Dmitry Lovetsky/AP Photo)

Somalis carry a civilian body who was killed in a car bomb which was exploded outside a restaurant in Mogadishu, Somalia, Tuesday, April ,21 , 2015. A car bomb killed people and injured several others at a restaurant in Somalia's capital on Tuesday, police said. Security forces have secured the area around the Banoda restaurant in Mogadishu, said senior police officer Mohamed Abdi. The car with the bomb was parked near Somalia's presidential palace, he said. (Photo by Farah Abdi Warsameh/AP Photo)

Cyclists lie in the street as they take part in a “die-in” vigil in memory of cyclist Moira Gemmill who died after being hit by a tipper truck on April 9, on a roundabout on the junction of Millbank and Lambeth Bridge in central London, Monday, April 20, 2015. Gemmill, aged 55 and the former head of design at the Victoria and Albert Museum, was the fifth cyclist killed in a collision with a vehicle in London this year. (Photo by Matt Dunham/AP Photo)

A seagull flys over a sea of poppies blanketing Federation Square as part of the 5,000 Poppies project to commemorate the centenary of ANZAC, in Melbourne, Australia, April 24, 2015. Upcoming April 25, 2015 marks the centenary of the landing of Australian and New Zealand Army Corps (ANZAC) troops at Gallipoli during World War I. (Photo by Tracey Nearmy/EPA)

A child weeps at a shelter for victims of immigrant attacks in Johannesburg, Wednesday, April 22, 2015. No new incidents of violence targeting foreigners were reported overnight in Johannesburg or in the coastal city of Durban, where the attacks began, police said. (Photo by Denis Farrell/AP Photo)

Three of the seven aircraft Breitling Jet Team fly their L-39C Albatros jets in formation and inverted over central Florida ahead of the start of their inaugural American Tour on Wednesday, April 22, 2015. The team, based in Dijon, France, representing the independent Swiss watch company Breitling, will be make their first public North American appearance at the SUN 'n FUN Fly-In & International Expo at Linder Airport in Lakeland Florida on Friday, April 24 and Saturday, April 25, 2015. (Photo by Katsuhiko Tokunaga/Breitling via AP Images)

A robot playsa the ball during a soccer match at the RoboCup German Open 2015 in Magdeburg, Germany, Friday, April 24, 2015. Around 200 teams from 14 countries demonstrate the state-of-the-art in robotics with competitions such as soccer, rescue and service robots. (Photo by Jens Meyer/AP Photo)

A robot plays the ball during a soccer match at the RoboCup German Open 2015 in Magdeburg, Germany, Friday, April 24, 2015. (Photo by Jens Meyer/AP Photo)

Iranian student Hafez Farazi of the German university Bonn codes his robot on the soccer field at the RoboCup German Open 2015 in Magdeburg, Germany, Friday, April 24, 2015. (Photo by Jens Meyer/AP Photo)

A robot sits between the students at the RoboCup German Open 2015 in Magdeburg, Germany, Friday, April 24, 2015. (Photo by Jens Meyer/AP Photo)

A woman wearing a sombrero with her face painted shouts during a march in Johannesburg, South Africa, Thursday, April 23, 2015, protesting against recent attacks on immigrants that killed seven people. The protesters walked through the center of Johannesburg passing neighborhoods that are home to many immigrants, a large number of whom come from other African countries. (Photo by Themba Hadebe/AP Photo)

The Dallas Cowboy cheerleaders perform on the red carpet at the 50th annual Academy of Country Music Awards at AT&T Stadium on Sunday, April 19, 2015, in Arlington, Texas. (Photo by Jack Plunkett/Invision/AP Photo)

The Dallas Cowboy cheerleaders perform on the red carpet at the 50th Annual Academy of Country Music Awards in Arlington, Texas April 19, 2015. (Photo by Mike Stone/Reuters)

A woman walks between balloons part of an art light installation in Bucharest, Romania, Thursday night, April 23, 2015. Bucharest hosts the Spotlight International Light Festival for the next three days. (Photo by Vadim Ghirda/AP Photo)

Schoolchildren perfom during celebrations to mark 35 years of Zimbabwe's Independence at the National sports stadium in Harare, Saturday, April 18, 2015. President Robert Mugabe, 91, the central figure in Zimbabwean politics 35 years after Independence from Britain, has led the country since 1980. (Photo by Tsvangirayi Mukwazhi/AP Photo)

Whitworth University students Melia Deters, top, and Skyler Noble, take advantage of the warm weather to study in their hammocks strung between pine trees on campus, Monday, April 20, 2015, in Spokane, Wash. “I like being in fellowship with people, and when you're in hammocks, it makes it even cooler”, said Deters. (Photo by Colin Mulvany/The Spokesman-Review via AP Photo)

A child runs pass burning tires during the xenophic violence, on 17 April 2015 in Jeppestown area of central Johannesburg. Twelve people were arrested overnight as anti-foreigner attacks in South Africa spread to parts of downtown Johannesburg, police said. According to local reports, the protesters from a local hostel demanded foreign nationals leave South Africa, setting cars alight and clashing with police. (Photo by Mujahid Safodien/AFP Photo)

Iranian soldiers in full camouflage march during the Army Day parade in Tehran on April 18, 2015. Amid rising tension between Iran and Saudi Arabia, Iranian President Hassan Rouhani said that Iran's military is purely for defence and should not be seen as an aggressive threat in the Middle East. (Photo by Behrouz Mehri/AFP Photo)

Palestinian children pose for a picture on a makeshift boat made of plastic bottles on April 18, 2015 at the port of Gaza City. (Photo by Mohammed Abed/AFP Photo)

Ruthie Jager, left, Caroline Jager, center, and Aubrey Peacock, right, all of Birmingham, Ala., react to a photo after singer Nick Jonas took a selfie with Caroline Jager's phone on stage during a Corner Block Party at Auburn University, Saturday, April 18, 2015, in Auburn, Ala. (Photo by Brynn Anderson/AP Photo)

An albino child sits between his parents in the traditional authority area of Nkole, Machinga district, on April 17, 2015. Six albinos have been killed in the poor southern African nation since December, according to the Association of Persons with Albinism in Malawi. (Photo by Gianluigi Guercia/AFP Photo)

A couple and their dog ride a motorbike with a side-car in the village of Nikishino on April 21, 2015 in the self-proclaimed Donetsk People's Republic (DNR). Only a handful stayed during the fighting here and as people returned to the village counting some 450 houses they found some 240 of those reduced to rubble or had been destroyed beyond repair. (Photo by Odd Andersen/AFP Photo)

A surfer watches turbulent seas at Avoca Beach on the Cntral Coast on April 22, 2015 in Sydney, Australia. Three people have died and more than 200,000 are still without power as cyclonic winds and rains continue to lash the Sydney, Hunter Valley and Central Coast regions of New South Wales. (Photo by Tony Feder/Getty Images)

Russian soldiers march during a rehearsal of the Victory Day Parade in Alabino, outside Moscow, on April 22, 2015. The parade will take place on Moscow's Red Square on May 9 to commemorate the 1945 defeat of Nazi Germany. (Photo by Kirill Zykov/AFP Photo)

Pro-Russian separatist Junga (war name) and his bride walk along river Kalmius after getting married in Donetsk on April 22, 2015 in the self-proclaimed Donetsk People's Republic (DNR). (Photo by Odd Andersen/AFP Photo)

A woman leans to peek into a chasm as Armenian people gather during a commemoration ceremony at a site called “Dudan” near Diyarbakir, and believed to be a mass grave of the Armenian Genocide, on April 22, 2015. Armenians prepare to commemorate a hundred years since a genocide wiped out up to 1.5 million of their kin as a fierce dispute still rages with Turkey over one of the greatest crimes of the 20th century. (Photo by Ilyas Akengin/AFP Photo)

A members of National Disaster Response Force carries an injured child, found under the debris of a residential building, to an ambulance, in New Delhi, India, Wednesday, April 22, 2015. One man and a child were killed and at least nine others were injured when a three-story residential building collapsed following an explosion in a cooking gas cylinder, according to local news agency Press Trust of India. (Photo by Manish Swarup/AP Photo)

Local people console a shocked mother whose child was found under the debris of a residential building, in New Delhi, India, Wednesday, April 22, 2015. One man and a child were killed and at least nine others were injured when a three-storey residential building collapsed following an explosion in a cooking gas cylinder, according to local news agency Press Trust of India. (Photo by Manish Swarup/AP Photo)

A aerial view shows a damaged mosque and surrounding buildings in the Al-Maysar neighbourhood of Aleppo, April 23, 2015. (Photo by Hosam Katan/Reuters)

In this Sunday, April 13, 2015 photo, Arab newscaster Lucy Aharish, seen through a viewfinder, speaks during an interview with The Associated Press in Tel Aviv, Israel. The 34-year-old journalist will be challenging some of her Arab compatriots who commemorate Israel's independence day as “the catastrophe”, when many Arabs were uprooted from their homes in the 1948 war surrounding Israel's founding. She also will be thumbing her nose at some Jews who believe she doesn't deserve the honor. (Photo by Ariel Schalit/AP Photo)

Alfie Ward dressed as Little Iron Man poses in front of the UK's largest LEGO statue as it is unveiled at the London premiere of LEGO Super Heroes: Marvel's Avengers Age of Ultron at Westfield Shopping Centre, London, on Tuesday, April 21, 2015. The life-size Hulk Buster Smash model stands over 2.5 meters high, 2.3 meters wide, weighs a ton and took six professional builders over 960 hours to create with over a million LEGO bricks, the most for any LEGO statue built in the UK. (Photo by Fiona Hanson/AP Images for LEGO)

Philippines' Katharina Lehnert plays a shot against India's Ankita Raina during the Fed Cup Asia-Oceana Group II Tennis Championship final in Hyderabad, India, Saturday, April 18, 2015. Lehnert beat Raina 2-6, 7-5, 7-5. (Photo by Mahesh Kumar A./AP Photo)

Two boys watch as a Russian-backed rebel convoy rolls along the street of Stakhanov, eastern in Stakhanov, Ukraine, Friday, April 24, 2015. (Photo by Mstyslav Chernov/AP Photo)

In this Monday, April 20, 2015 photo, a Bangladeshi man walks near a monument erected in memory of the victims of Rana Plaza building collapse, the worst in the history of the garment industry in Savar, near Dhaka, Bangladesh. Human Rights Watch has criticized the Bangladeshi government for failing to protect workers, saying not enough is being done to eliminate assault, intimidation and other abuses still common in the garment industry. Bangladesh suffered its worst industrial disaster when Rana Plaza, an illegally built, multistoried building located outside of Dhaka, Bangladesh's capital, collapsed in 2013 killing 1,127 people and injuring about 2,500. (Photo by A. M. Ahad/AP Photo)

An African migrant smokes outside Holot detention center in the Negev Desert, southern Israel, Tuesday, April 21, 2015. Tens of thousands of African migrants have made their way to Israel in recent years. Most of these migrants came from Eritrea, an eastern African nation with one of the world's most dismal human rights records. (Photo by Tsafrir Abayov/AP Photo)