Interactive 3D IPython Rendering

As far as I know, the only cheminformatics library with IPython notebook support is RDKit, which renders its objects as 2D pngs. Rather than copying that, I thought we could try to one-up it :-)

Right now, this PR is a *very* rough implementation of interactive 3D rendering. It uses [three.js](http://threejs.org/) and [this drawer I made](http://ec2-184-73-149-254.compute-1.amazonaws.com:9000/). To use, clone my fork and make sure that `openbabel/scripts/python/pybel` is in the same directory as `pybel.py`.

I want to gauge interest on functionality like this before cleaning up my code. Does anyone think this is a good idea? Does anyone want to help?

**Example:**

![screen shot 2013-09-29 at 5 50 41 pm](https://f.cloud.github.com/assets/1449833/1234085/23cdf024-295a-11e3-9e1b-03ee8dd7a482.png)