Adding a custom 404 page.

This custom 404 page gets called 2 different ways:

1. If you call `render_error_page(404)` from one of the controllers
2. I added a catch all route to the end of the routes file that routes to `application#routing_error`

This completes DIR-103

The error looks like this:
 
![screen shot 2014-09-05 at 9 28 18 am](https://cloud.githubusercontent.com/assets/957859/4168189/b95e8e0c-3519-11e4-9bfc-5d1b79255f08.png)