use ansi-to-html to get colored output

This addresses issue moxley/atom-ruby-test#8

This is my very first attempt to contributing anything to atom (actually my first attempt to do anything with node.js at all) so all feedback is welcome.  The current test suite runs for me, but the spec about the resize handle is failing on the current master branch.

I didn't write any tests for my code since I literally have no idea what I am doing, but if you are inclined to merge this I would be happy to go back and be more thorough.

This is what the output looks like for me right now:

![screen shot 2014-05-19 at 9 45 37 pm](https://cloud.githubusercontent.com/assets/80008/3022745/a25fbfe8-dfd1-11e3-96f6-3ac7d197e02c.png)