Modified "rainbow" color scheme

This release is a small modification from the previous release, the colour scheme named "rainbow" has been modified to be more aesthetically pleasant.

Upgrade according to reviewers comments after JOSS submission

Plots are automatically re-drawn when changing graphical parameters.
"Select all" option to select all genotypes for statistical testing.
Creation of a pip package.

First release

v0.8.1

correct typo in README.md