Small changes*.

* Not really. A complete overhaul. Moved tons of files around, changed
the primary pdf renderer, fixed up CSS, ... Really got everything
working.

docy.py will render a markdown file to a pdf formatted as MLA.

Added metadata support to markdown files. It can take the form of

---- example.md ----
key: value
key2: value

... h1 stuff and stuff ...
--------------------

The blank line is required, even if no metadata is present.