Reviewed by GREG KINGDirectors: Henry Joost and Ariel SchulmanStars: Emma Roberts, Dave Franco, Emily Meade, Miles Heizer, Juliette Lewis, Machine Gun Kelly, Brian Marc, Marc John Jeffries.Nerve is a popular on-line social media game in which competitors are set challenges, a bit like an internet version of Fear Factor. The more dangerous the challenge the more money a person can make, but if you fail …