add template for IPython notebook CodeMirror

Hello Chris. I'm a major fan of your color schemes (particularly Ocean). I wanted to be able to use them in [IPython Notebook](http://ipython.org/notebook.html), a tool I use frequently. Because IPython Notebook uses CodeMirror, I simply added a good chunk of IPython-specific styling to @idleberg's CodeMirror template.

I have [my own repo](https://github.com/nsonnad/base16-ipython-notebook) with the rendered css files and a readme on how to get them working. Let me know if you have any issues or questions, thanks!