bash-setup: missing explanation

[buhtz]

This is about this section of your documentation
https://github.com/b-ryan/powerline-shell#bash

The bash code is without in-line comments. The text before the code does not explain the code.
So it is unclear what the code does. Bash is not self explaining.

It would improve the documentation if you could add one or two short sentences about what this code does. Thank you very much.