Allow bot to host multiple games

[RailKill]

Currently the bot creates a single game instance when it starts. We can grow this bot to host multiple games. Perhaps the game instance should be bound to the channel it was started in, so it's like one game per channel?

Doing so will also allow the bot to serve multiple servers which opens up the possibility of it being hosted and listed in discordbots.org to be used by people all over the world. Pretty cool!