Remove powerline module.

The developer's branch changed, so now "master" is an empty branch.
Re-add Powerline plugin.
Steal a bunch of stuff from Janus to customize some plugins.
Add HAML and CoffeeScript file support to ack.
Disable vimpager from being the pager.
Lots of vim tweaks, mostly around working with powerline and nerdtree.
Change ZSH path to Powerline bindings.