add powerline to bundle

I wanted to add powerline to streamline my vim experience while working
on a project.
organize local bundles

It the interest of keeping this organized I separated the bundles into
groups dedicated to the role they are providing with a brief comment
above them. This isn't necessary right now, but I'd rather start with
good practice now.
Merge pull request #14 from zachmokahn/vimrc_bundle_local

Vimrc bundle local