Switch from pathogen to NeoBundle
Use g by default with Vim find and replace
Use prezto's dot expansion
Upgrade prezto
Expand $PATH to multiple lines

By adding paths to `$PATH` one at a time it's easier to track changes.
It's also easier to spot duplicates, as is the case with
`/usr/local/bin`, one of which is being removed here.
Overhaul Makefile

This is such a large overhaul of my Makefile that it's going to be
really hard to capture everything that has been changed, but the
important things are:

    - Reorganized commands within Makefile to make things more modular
    - Switch from Homebrew's Ruby to rbenv
    - Use the pip installable version of Powerline