A prototype Rollkers transportation device is displayed during a press event at the Mandalay Bay Convention Center for the 2015 International CES on January 4, 2015 in Las Vegas, Nevada. The product is not a skate; it balances for you and when you place it on the bottom of your shoe, it gives you the ability for faster transportation based on walking. The balance CES, the world's largest annual consumer technology trade show, runs from January 6-9 and is expected to feature 3,600 exhibitors showing off their latest products and services to about 150,000 attendees. (Photo by Ethan Miller/Getty Images)

A large molded bust of Edward Snowden is pictured in Fort Greene Park at the Brooklyn borough of New York in this April 6, 2015 picture provided by ANIMALNewYork. A group of anonymous artists erected the 4-foot-tall bronze statue of Snowden, the former U.S. spy agency contractor famous for leaking classified information, in a New York City park overnight, officials said on Monday. (Photo by Aymann Ismail/Reuters/ANIMALNewYork)

Abandoned cars are seen around a cross in the village of Tbeti near Tskhinvali, the capital of the breakaway region of South Ossetia, Georgia, July 4, 2015. President Vladimir Putin signed a treaty with Georgia's rebel South Ossetia region on March 18 that almost completely integrates it with Russia, alarming Georgia and the West a year after Moscow took over Crimea. Russia won a five-day war with Georgia in 2008 over the fate of South Ossetia and another rebel region, Abkhazia. It formally recognizes both regions as independent states and signed a similar treaty with Abkhazia last year. (Photo by Kazbek Basaev/Reuters)

An Airbus A400M military aircraft lands at the ILA Berlin Air Show in Schoenefeld, south of Berlin, Germany, June 1, 2016. The Aerospace Exhibition at Schoenefeld Airport near Berlin takes place from June 1 till 4. (Photo by Fabrizio Bensch/Reuters)

Mike Branch helps customers shop for a Halloween masks at Fantasy Costumes on October 28, 2011 in Chicago, Illinois. The store, which had long lines at the registers at 4 AM this morning, is open around the clock through Halloween to help keep up with customer demand. Retailers nationwide are expecting record sales for Halloween merchandise this year with shoppers spending close to $7 billion dollars to celebrate the holiday. (Photo by Scott Olson/Getty Images)

The London 2012 ArcelorMittal Orbit Sculpture at the Olympic park nears completion on November 4, 2011 in London, England. The Ј22 million sculpture designed by Anish Kapoor is nearly complete. Standing at 115 meters tall the permanent structure is Britain's largest artwork and houses an observation deck near the top. (Photo by Peter Macdiarmid/Getty Images)

Chinese Panda Yang Guang arrives at Edinburgh Airport on December 4, 2011 in Edinburgh, Scotland. Tian Tian and Yang Guang, a pair of eight-year-old giant pandas arrived on a specially chartered flight and will be the first to live in the UK for 17 years. Edinburgh Zoo are hopeful that the pandas will give birth to cubs during their 10 year stay in Scotland. (Photo by Jeff J Mitchell/Getty Images)

Cathryn Shrimpton, 4, prepares to play the Angle Gabriel during a traditional Christmas Nativity on December 18, 2011, at St Mary's Church, Myton Village, England. In schools and churches around the country children busy preparing and performing in the telling of the traditional nativity story. (Photo by Bethany Clarke/Getty Images)