Feature/documents

Polymorphics... STIs...

Tried to cleanup the models, but that turned even messier.

I will probably go back and fix it once we nail down the feature sets.

![tumblr_m26nvnng5o1qkk10ro1_500](https://cloud.githubusercontent.com/assets/1641464/3197048/4a2d9d24-ed3f-11e3-9f71-afb6915f0e13.jpg)