Automatically generate output from notebooks

Added functionality to automatically generate docs from notebooks. The only necessity is that the notebook has to have a "heading" of some sort in the first cell, so I can give sphinx  a title for the linked document. All notebooks in examples/notebooks are added to the docs.

It takes the input-only .ipynb, runs them and gets the output, then uses nbconvert in a way very similar to nbviewer to generate HTML, which is placed into a `raw` directive in a sphinx document. Runs only on Python >= 2.7. Requires nbconvert and IPython.

Tested locally, but will need to update the paths once it's merged (or before) to be general and to fail gracefully, so we don't require the unstable nbconvert to build the docs. I'm not positive that the hard-coded CSS paths in the javascript will work, but it's not too a huge deal if we have to include the new CSS in all the pages not just these. 

Might also want to add a link to the .ipynb source on github somewhere in the document but likely not in this PR.