Importnb

* Update importnb to work with Python 3.8 nightly builds
* Make parameterize optional
* Remove the notebooks sources.

python -m pytest index.ipynb --doctest-modules --nbval --monotonic

Will check all doctests in Code and Markdown cells, check the input and output of cells, and assure that the execution order is monotonically increasing.

The notebooks need to go away after there is a better CLI to bump a new version.

Pytest has an `--nbsource` option to test the state of notebooks.
Parameterize permits boolean parameters.
Docs are on read the docs.