Let users log out

--verifying that users don't have the same name will be done through coffeescript with pusher
I'm not sure how to extract ```allowed_to_visit``` or ```current_handle``` into a separate class. Since RoomSessionsController initializes a RoomSession, how is RoomsController supposed to access any of the room_session objects that are active to check if someone is allowed to access a room? should I write a bunch of class methods?