Remove local shoes-highlighter in favor of its own repo

Removed the shoes-highlighter from this repository and moved it over to [shoes/shoes-highlighter](https://github.com/shoes/shoes-highlighter) - everyone should have the appropriate organization access rights etc. over there, if not please let me know.

I already pushed the gem to ruby gems: https://rubygems.org/gems/shoes-highlighter

@jasonrclark @wasnotrice I added you as gem owners.

Of course, this all is just building off the splendid of @jasonrclark without whose work this wouldn't have been possible.