Add a handler to catch SIGINT/^C to the server, to inform clients that the server is going down and cleanly disconnect them. Clients alert the user and clean up a bit (but a significant amount more cleanup could probably be done)
Actually, cleaning up KNOWN_PLAYERS on the client is necessary, and I forgot that I already had app.disconnect as a thing, so I just went through that code.
Merge pull request #4 from dylanryan/clean-server-shutdown

Clean server shutdown