Vendor the css and refer to it instead

We were linking to `http://jashkenas.github.io/docco/resources/linear/docco.css` but that has changed a lot and the examples all look horrible now.  This should fix it.
Hm, yeah, I'm sure there's a good way to do this, I'm just a little rusty on how this library works exactly. The main issue is that there are example files in both `ex/file` and `ex/network/file` so relative links don't work without more magic. I have to make them absolute. but that means that I have to hardcode the `libgit2` in there I believe (like `/libgit2/ex/css.css`). So stupid.

It may actually be easier to just slap the css itself into this template file rather than linking it. Not super efficient, but it's simpler and bulletproof.