Major Site Revamp

This is probably a little more major than is strictly necessary, *but*
it does set up a pretty good framework for building in the future.

I added Bootstrap (actually a Bootswatch theme) so it's pretty without
having to spend too much time making it look good. The benefit of this
is that just about everything you'll want to add in the future will look
good with this. I'm getting Bootstrap (css and js) from a CDN. Note that
the version of jQuery I'm using isn't compatiable with old versions of
Internet Explorer (but, since this is an OS X app, I doubt if that's a
big problem users will face).

I also moved just about everything that I could out into includes. This
makes it a lot easier to modify things in the future, since you've only
go to do it in one place.

As of now, to the best of my knowledge, everything works except the
documentation. The reason that the docs don't quite fit with the rest of the site is that I'm not sure how the process for all of that works. The easy fix would be to modify the template.erb files used to generate those to look like the default layout generated by jekyll.

Some of the local jekyll testing is kind of funky. I remember this being
a problem when working on my personal site, but I don't really remember
the resolution. The big place to watch for this being a problem for hammerspoon is the release notes detail pages. 

![hammerspoon](https://cloud.githubusercontent.com/assets/1231554/4753253/807fcdd2-5ab5-11e4-88bd-bf1cd37dd9cf.gif)