Allow bot to join channels with passwords

[sterlingalexander]

Currently, if the bot is to join a channel with a password, the channel operator needs to remove the password, invite the bot, then re-add the password. It would be nice to add the ability to join a password-protected channel.

[tiwillia]

This is actually already done for the most part. The bot can join a channel by telling it:

bot_name, join #chan <pass>

However, the bot cannot join channels with passwords automatically on start-up. We'll need a config option of some sort stored alongside the channel. Probably just going to have to create a channel model.