.zshrc: Set up basics, inspired by zsh-newuser-install and compinstall.
.zshrc: Configure prompt, ls (for BSD), and grep.
.zshrc: Configure git aliases, similar to .bash_profile.
.zshrc: Set up git autocompletion.
.zshrc: Configure Ruby variables and aliases.
.zshrc: Set up rbenv.
zsh: Set ZDOTDIR and EDITOR in .zshenv instead.
.zshrc: Improve interaction with $fpath.
.zshrc: Set up git-prompt.
Merge branch 'switch-to-zsh'