NBC Sports is launching on Snapchat in advance of the NHL’s annual “Winter Classic” on New Year’s Day. The NBC Sports Snapchat account, which goes live today, will be a behind-the-scenes hub for hockey fans to show how Gillette Stadium is transformed from a football field to an outdoor hockey rink. It will also take viewers into NBC Sports’ production trucks and down to the rink as the broadcaster prepares to televise the event…