Adds initial version of IIIF OpenSeadragon image viewer plugin

Closes #11, #65, #92

Test object - http://purl.stanford.edu/cn006dx2288

![image](https://cloud.githubusercontent.com/assets/302258/4890703/50ed5860-63a1-11e4-975f-05cdae5263c4.png)
![image](https://cloud.githubusercontent.com/assets/302258/4890710/5bb97c74-63a1-11e4-87da-a1ac52ef1a78.png)
![image](https://cloud.githubusercontent.com/assets/302258/4890712/64d3c51c-63a1-11e4-9e20-f923cc7c8bf2.png)
![image](https://cloud.githubusercontent.com/assets/302258/4890720/76b26d56-63a1-11e4-9c0e-77b4352a0807.png)

Pending features in IIIF viewer plugin : 
- [ ] lazy loading in all views
- [ ] links between views
- [ ] remove thumbs container for single image (in list view)

I'll create separate tickets for pending features. 

All these full screen selectors seem to be doing the same thing, can we just comma separate them?