Add report functionality to sits

Made some good progress on allowing users to flag inappropriate content. I had some trouble breaking up the `db/structure.sql` file. I guess there were some things in there that have been removed, and the file never got updated?  Let me know if you have any thoughts!

![screenshot 2014-12-18 16 08 26](https://cloud.githubusercontent.com/assets/816517/5495970/6c290d84-86d0-11e4-9e37-fa1593a39f81.png)

![screenshot 2014-12-18 16 09 29](https://cloud.githubusercontent.com/assets/816517/5495972/6ff1a4f8-86d0-11e4-9e9c-5b544fe27fa0.png)