Bot now uses chans={set of chans} rather than join="#chan1,#chan2" and handles chans sanely.
In particular self.chans is a set of chans the bot is currently on. It gets updated by the join and part methods, and is also updated when the bot gets kicked.
Merge branch 'master' of github.com:asv-github/bp4u-irc-bots

Conflicts:
	bot.py