Enable Travis CI notifications

This commit enables notifications to the following communication 
channels:

* HipChat - "Build Statuses" and "Open Source" rooms
* IRC - #chef-hacking channel
* Gitter IM - opscode/chef chat room

Notifications will only be sent if a build fails OR a failed build 
transitions to successful.
Merge pull request #1287 from opscode/enable-travis-notifications

Enable Travis CI notifications