Allow unbalanced teams

[dblock]

See AlexLaviolette@4b0c77a.

[AlexLaviolette]

Currently in our office we use slack-gamebot for a Rocket League ladder.

There are some pretty large skill discrepancies between players which makes for some pretty competitive and balanced 2v1 or 3v2 matches - allowing unbalanced teams lets us increase the stakes and fun for those type of matchups.

[dblock]

Thanks @AlexLaviolette. I'll add a set command that makes balanced games optional for a team. You can of course beat me to it and contribute :)

Also #126 could help with nomenclature of the bot, lots of people use it for all kinds of non-ping-pong or chess type things.

[dblock]

Implemented in bd75353.