Bring down the server on (some?) uncaught errors.
Bring down the server on (some?) uncaught errors.

I added an errback to the LoopingCall for gameStateManager.tick, so
it'll be called if any exception gets raised out of one of those calls.
The errback just prints a traceback and then brings down the server,
ensuring that other clients get disconnected as well.

This is at least some progress on #31, though it's hard to know if the
issue is really fully fixed.

CheeseLord/warts,CheeseLord/warts