adds Rematch handler in game Chat
adds RematchOffered, RematchDeclined and Rematch in Game and handles corresponding messages
adds offer or accept/decline rematch methods in Game
adds user parameter to Game
removes user parameter from getUserColour and refactors it to calculate on init instead of every time
removes user argument from getUserColour() call in GamePage
corrects reference to _game.offerOrAcceptRematch in GamePage
moves _getUserColour after _players have been defined in Game
binds callback for template event in GamePage