Implement nickserv auth in hubot-irc adapter

We need a way to run privileged commands in the public IRC channel.

There is some information on security during IRC netsplits that is worth reading on [wikipedia](http://en.wikipedia.org/wiki/Internet_Relay_Chat_takeover), however, it seems this is no longer much of a concern now that services (like NickServ) are common.

### Notes

- We should investigate the `KILL` and `SECURE` settings for NickServ before giving hubot any responsibility: http://wiki.swiftirc.net/index.php?title=Nickserv#Kill

### Todo

- [ ] get nickserv auth working (nandub/hubot-irc#103)
- [x] create no-op demo script