Highlight the code entered on the homepage

When a user enters code into the textarea on the homepage, it's sent via AJAX to the ParsesController and returned with highlight classes applied. The code also re-highlighs if the user changes the language.

Also:

- [x] Added an .rspec file so it automatically includes `spec_helper.rb` ([Blog Post](http://robots.thoughtbot.com/document-explicit-dependencies-through-tests))
- [x] Added an apple-touch-icon PNG's so safari won't log an error when it goes looking for them ([StackOverflow](http://stackoverflow.com/questions/12480497/why-am-i-getting-error-for-apple-touch-icon-precomposed-png))
- [x] Added the base16 theme. I'll probably change this though. I'm thinking about making a custom rouge theme. We'll see if it shows off the highlighting enough though...

TODO:
- [ ] Handle parse errors in rouge (I might open an Rouge issue as I have some ideas on this one)
- [ ] Make a rouge theme?