Updates README to mention that need to set PROXIED on Heroku.

This could also be easy to miss, and result in deployments with
ineffective vote limiting.
Merge pull request #19 from jeremybanks/read-this

Update README to mention the need to set PROXIED on Heroku.
Allow the IRC channel, nick, and URL to be specified in environment variables.
Merge branch 'irc-envs' into ng-showbot
Use same hostname and port for WebSockets when non-local.