Convert lobby from polling to sockets

Now while waiting in the lobby, it no longer polls every 5 seconds and reacts to socket events instead. Games list will update when new games are added and when players join existing games.

Created a socket channel called lobby dedicated to this, so that messages are only sent to users in the lobby.

Also removes players from a game if they disconnect and kills the game if they are the last player to depart.

This is currently deployed to http://humanity.azurewebsites.net/ if you want to try it out first.