Reduce PyMKS repository size

[Daniel Wheeler]

I ran the BFG repo cleaner
[https://rtyley.github.io/bfg-repo-cleaner/] on PyMKS and it reduced
the size of the repository to 46M from its current size of 258M. There
were 5 big files that got removed.

Filename Git id
---------------------------------------------------------------------------------------------
05 - Improving Performance.ipynb | be79fee7 (36.8 MB)
06 - Improving Performance.ipynb | 286ef30d (36.8 MB), be79fee7
(36.8 MB), 1e3e2cd6 (36.8 MB)
cahnHilliard4.ipynb | ea23d4d0 (47.7 MB), 2b3b6d38
(32.6 MB), ...
sandbox.html | 9d1c6ab1 (22.8 MB)
sandbox.ipynb | 825e4b8a (26.9 MB), d33f7f43
(26.9 MB), ...
sandbox.txt | 71a8bb8d (23.9 MB)
searchindex.js | 403c89fd (23.8 MB)

The new clean repository is here

https://github.com/wd15/pymks-clean

It obviously speeds things up a lot in terms of cloning the repository
and that can be quite a big deal in a workshop environment when people
are all using the wifi from their laptops.

This does change the commit SHAs so all developers need to be aware
that they need to abandon the old repository and checkout the new one
before continuing their work and make sure that any open branches are
pushed to materialsinnovation/pymks before I make the switch.

My opinion is that we should do this and make sure we're cognizant of
not adding large files in the future. Especially check the size of
notebooks before adding them to the repository.

Cheers,

Daniel

--
Daniel Wheeler