Calls out irc as package dependency

Running bin/hubot failed on my machine because I didn't have the "irc" node module installed.

Calling "irc" out as a dependency in package.json installs it automatically when you do a bin/hubot if it's not there already.

I locked the version to >= to what ```npm install irc``` pulled down (0.2.1).  Hope that's cool with you.  It seems to work OK.