Clean up README. Make it barebones information about installation and use, and a link to the full docs. The full docs for the project will live on design nonprofit site

[StevenTammen]

Mention the xonsh shell, the vox xontrib, and the bit in my .xonshrc that automatically adds all project directory paths (that is, all things in general format ~/projects/some-project-dir) to my $PATH.

I like this better than having scripts directly in like ~/.local/bin since everything is fully version controlled and separable. I think it scales better.