GitLab

Based on Evan's prompt, it uses colors, shows the exit status of the
last command if it was non-zero, and displays "#" when running
with elevated privileges

This means we are running it after $PATH has potentially been set up,
which means it's more likely that commands like "git" will be found

Moving all zsh config options into a lib/ subdirectory to make way for some upcoming changes to directory structure and configuration options

`git-symbolic-ref` needs to be `git symbolic-ref`

 * Improved speed, the first time cd'ing into a git repo the prompt
   returns much faster (for me at least).
 * Prompt is now decorated in nested folders within a git repo. No
   longer check for the '.git' folder.