Choose a tool to simplify diffs on .ipynb files.

[andrewphilipsmith]

trafficstars

Consider

• https://www.reviewnb.com/
• https://jupyter.org/enhancement-proposals/08-notebook-diff/notebook-diff.html
• https://blog.ouseful.info/2017/01/27/displaying-differences-in-jupyter-notebooks-nbdime-nbdiff/

and others

Build into workflow using pre-commit/CI as appropriate.

[andrewphilipsmith]

Have applied ReviewNB to this repo.

We should review it after a separate independent PR has gone through.