adds in tooltip for stanford only files

Uses twbs tooltip.js library (some classes slightly modified to add `sul-embed` prefix)

Closes #62

![screen shot 2014-10-17 at 3 35 21 pm](https://cloud.githubusercontent.com/assets/1656824/4687061/ea4bafea-564d-11e4-9203-1b575f0d3626.png)

Yep I know thats the spec, but I'm going rogue here. The interaction at the entire div level felt way off. If it something we need to do we can add back, but I felt this was better.