Added new WebGL demo

WebGL molecular viewer in the notebook.
[Video demo here](https://www.youtube.com/watch?v=4fnheP83pzY).

Ready to review/merge.

![Screenshot](https://cloud.githubusercontent.com/assets/1942359/5008634/b24c9eea-6a5e-11e4-8706-a9d4004f023b.png)