Switch to Jekyll

Switches to Jekyll, where HTML is generated upon deploy. Coming from a system powered by the [DocumentUp](http://documentup.com/) API plus a `compile.rb` script, where HTML was frozen into the repo.

Changes:

* New pygments theme, taken from [MozMorrow/tomorrow-pygments](https://github.com/MozMorris/tomorrow-pygments). (`.err` class disabled, to allow for ellipses.)
* Switched fenced code block syntax to Jekyll (Liquid) syntax, for Jekyll-level pygments highlighting.
* TOC is now generated upon demand, but is generated in each page -- and then copied via JS upon page load. (Awful hack.)
* Each page now has a tiny bit of YAML front-matter at the top, specifying the default layout.

I wrote a [small adapt.rb script](https://gist.github.com/konklone/7935945) that can be run on all `.md` files in a directory to transform them from old to new style.