Install NBDIME notebook diff plugin

[delgadom]

Package descriptions:

• https://github.com/jupyter/nbdime
• https://nbdime.readthedocs.io/en/latest/extensions.html

This is working its way into a core jupyter feature (but looks like it's likely pretty far off):

• https://github.com/martinal/enhancement-proposals/blob/7ea2c63cf89953e75e5b9f56fc28143406e3b3d6/notebook-diff/notebook-diff.md