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 work by Chinese artist ROBBBB is seen on a wall in the ruins of a building in Beijing September 27, 2015. The 25-year-old artist in Beijing prefers to display his work on the walls of abandoned buildings, rather than a gallery. His artwork is mostly derived from photos of people he sees in the Chinese capital, anyone ranging from elderly people to construction workers. (Photo by Jason Lee/Reuters)

A Myanmar Shiite Muslim devotee runs barefoot over a bed of burning coals as he takes part in a Muharram procession ahead of the Islamic holiday Ashura, in Yangon, Myanmar, October 22, 2015. Muslims across the world are observing Moharram, the first month of Islamic calender, the climax of Moharram is the Ashura festival commemorating the martyrdom of Imam Hussein, a grandson of the Prophet Mohammed in the Iraqi city of Karbala in the seventh century. (Lynn Bo Bo/EPA)

A Tibetan pilgrim prostrates herself at the Jokhang Temple in central Lhasa, Tibet Autonomous Region, China early November 20, 2015. Every day thousands of Tibetans visit and pray at Jokhang Temple, considered one of the most sacred places of worship. (Photo by Damir Sagolj/Reuters)

First time gun owner, Jessie Palmieri holds a target she shot with a H&K VP9 9mm gun at the Ringmasters of Utah gun range, in Springville, Utah on December 18, 2015. (Photo by George Frey/Reuters)

A Thai traffic security guard wears a Santa Claus costume as he directs the traffic on a street during Christmas celebrations outside a shopping mall in Bangkok, Thailand, 22 December 2015. The campaign of a shopping mall is held to celebrate the upcoming Christmas season and to attract shoppers. (Photo by Narong Sangnak/EPA)

President Woodrow Wilson speaks on telephone. Woodrow Wilson was the 28th U.S. President serving from 1913 – 1921. (Photo by Corbis)

A spiritual leader (R) of the Huni Kui Indian tribe blows an herbal powder into the nose of a tribal member during a ceremony outside the village of Novo Segredo along the Envira river of Brazil's northwestern Acre state, March 9, 2014. Many indigenous groups, including the Huni Kui, Ashaninka, and Madija, live in villages in the Brazilian rainforest near the border with Peru. (Photo by Lunae Parracho/Reuters)