Transform notebooks into md files

[thorwhalen]

There's nbconvert already, but there's still some manual work to make it clean.

Known problems:

• style scoped html visible (in pandas dataframe displays): See image
• AxesSubplot:xlabel when displaying graphs
• images are saved in root level (in zip): More convenient to save them in an img folder to keep them out of view. Need to change the (e.g.) ![png](output_18_1.png) snippets to ![png](img/output_18_1.png).

Pre-dev research:

• nbconvert arguments
• existing github/pypi code to solve problem