A freighter trapped in ice is shown in this aerial photo near Whitefish Bay on Lake Superior northwest of Sault Ste. Marie, Ontario April 7, 2015. The biggest ice cover on the Great Lakes in decades is backing up shipments of everything from Canadian grain to U.S. iron and steel in one of North America's most important economic regions. (Photo by Kenneth Armstrong/Reuters)

In this photo released by Xhinhua News Agency, a rescuer evacuates residents near the site of a chemical plant blast in Zhangzhou, southeast China's Fujian Province Tuesday, April 7, 2015. Six people have been hospitalized and hundreds of firefighters deployed to battle a blaze sparked by an explosion at Goure PX Plant that produces the toxic chemical paraxylene, officials said Tuesday. (Photo by Wei Peiquan/AP Photo/Xinhua)

The chariot of God Bhairab is pulled through the city centre of Bhaktapur near Kathmandu during the Bisket festival April 10, 2015. The festival, which runs for more than a week and coincides with the Nepalese New Year, involves devotees offering prayers and the pulling of two chariots, one carrying the idol of God Bhairab and the other with the idol of Goddess Bhadrakali, around the ancient city of Bhaktapur. Devotees participate in the festival with the belief that they will be blessed with good health, fortune and harvest for the coming year. (Photo by Navesh Chitrakar/Reuters)

A lady-in-waiting adjusts the dress and Christian Louboutin shoes of Dayangku Raabi'atul 'Adawiyyah Pengiran Haji Bolkiah as Adawiyyah waits for Prince Abdul Malik to arrive for the “bersanding” or enthronement ceremony at their wedding in the Nurul Iman Palace in Bandar Seri Begawan April 12, 2015. Malik is the son of Brunei's Sultan Hassanal Bolkiah, one of the world's richest men. (Photo by Olivia Harris/Reuters)

A picture of Moon Ji-sung, a high school student who died in the Sewol ferry disaster, hangs in her room in Ansan April 7, 2015. Her dream was to be a flight attendant. Nearly a year after the Sewol ferry sank on April 16, 2014, with the death of 250 students, some families keep their children’s bedrooms intact to remember and honour their loved ones. More than 300 people, most of them students and teachers from Danwon High School, are dead, or missing and presumed dead, after the Sewol ferry sank on a routine trip from the port of Incheon, near Seoul, to the holiday island of Jeju. (Photo by Kim Hong-Ji/Reuters)

Senator Barack Obama (D-IL) (R) stands in front of Senator Hillary Clinton (D-NY) as they arrive for U.S. President George W. Bush's annual State of the Union speech to a joint session of Congress at the U.S. Capitol in Washington in this January 23, 2007 file photo. Hillary Clinton announced her second run for the presidency on April 12, 2015 starting her campaign as the Democrats' best hope of fending off a crowded field of lesser-known Republican rivals and retaining the White House. (Photo by Larry Downing/Reuters)

A humanoid robot named Kansei, meaning “sensibility” in Japanese, makes a facial expression depicting “happiness”, next to the word “Love” during a demonstration at a laboratory of Meiji University's Robot and Science Institute in Kawasaki, south of Tokyo in this June 4, 2007 file photo. Three-fourths of robot installations over the next decade are expected to be concentrated in four areas: transportation equipment, including the automotive sector; computer and electronic products; electrical equipment and machinery. Labor costs have climbed in countries such as China that have been popular for outsourcing production, while technological advances for robots allow them to be more flexible and perform more tasks. (Photo by Yuriko Nakao/Reuters)

A farmer is seen hanging from a tree during a rally organized by Aam Aadmi (Common Man) Party (AAP) in New Delhi April 22, 2015. The farmer hanged himself from a tree during a political rally in New Delhi on Wednesday, in what appeared to be a desperate protest against the hardship felt by many people scratching a living in rural India. Four people climbed the tree to try to save the man after he was seen hanging. (Photo by Adnan Abidi/Reuters)