.bashrc: Add invert code to ANSI color codes
.bashrc: Improve 'char' function
.bashrc: Add invert blue to color codes

Mostly just to serve as an example of how to invert foreground and
background using ANSI color codes.
.bashrc: Snazzify prompt

Note that the prompt really only works with the Source Code Pro for
Powerline font, available at [1].

  [1] https://github.com/Lokaltog/powerline-fonts
.bashrc: Support both pythonbrew and pyenv

I currently have pythonbrew installed on my work machine, and pyenv
on my home machine. Until I can upgrade to pyenv on my work machine
(or decide to restart my use of pythonbrew at home), support both
managers and dynamically select the one to use.
.bashrc: Remove duplicated (and commented-out) environment variable