Remove unused selection css in index

Nothing exciting here, but for some time I had noticed this referenced css does not exist and was generating console errors on launch on my local server.

`GET http://localhost:8000/app/css/select2.css 404 (Not Found) `

This PR removes that unused reference. With it removed, the console error is gone. I also checked to ensure there was no other possibly intended 'select' css in app/css. There doesn't appear to be any.

Tested on Windows:
FF Release **30.0**
Chrome Latest Release **35.0.1916.153 m**

Adding @jeads and @camd for visbility.