Failed install on Ubuntu 14.04

Installing on Ubuntu 14.04 fails since Rubygems is not available. Per [launchpad.net](https://launchpad.net/ubuntu/trusty/i386/rubygems/1.8.24-1ubuntu2) Rubygems is already included in Ruby.

I'm new with ansible so if there is a better way please let me know.

I've tested on fresh installs of Ubuntu 12.04 and 14.04.