Suggestions

This pull request allows people to add video suggestions to the site, and admins to approve them. I'm going to leave it here for a few days for comments / questions.

Particular things to note:
- new Suggestion model to house suggestions. right now only youtube videos, and a bunch of hardcoded assumptions there, but flexible for the future
- tweaks to match details pages to encourage adding videos
- new suggestions area of admin page

![screen shot 2013-06-01 at 9 29 16 pm](https://f.cloud.github.com/assets/57101/595903/1e35f1e6-cb3d-11e2-8dcb-a32f6b11f541.png)
![screen shot 2013-06-01 at 9 29 54 pm](https://f.cloud.github.com/assets/57101/595904/1e39cf14-cb3d-11e2-8cce-9f00e72601ae.png)
![screen shot 2013-06-01 at 9 29 10 pm](https://f.cloud.github.com/assets/57101/595905/1e517a1a-cb3d-11e2-9062-58a3bd7352a0.png)