Unregister and unbind modules from willie.bot when they are reloaded.

-Adds methods unregister and is_callable to willie.bot.
-Adds code required to remove references to willie callables, in modules
 themselves and willie, to willie.modules.reload.
Merge commit 'b47b88ee79f3b5586654c1da4653a81bbf77d37d' into reload_fix

Conflicts:
	willie/bot.py
Remove check for __hash__ and rename function parameter callable to variables.
Merge pull request #259 from Venti9874/reload_fix

Module reloading fix.