Use Jekyll for the docs

[Emanuel Rabina]

I'm not particularly fond of the manual process I have for building the documentation out, and it seems the longer I stay on gitbook without using their new paid service, the harder it is to keep them running as is. So I'd like to see if it can be simplified with Jekyll and a nice theme.

This one seems pretty good: https://pmarsceill.github.io/just-the-docs/