Make it Markdown

Filesystem conneg...meh...
Revert "Remove plugins from config"

This reverts commit 6bcc27541283692b159170102f2061f6ec40928a.

GitHub Pages *does* use these plugins:
https://help.github.com/articles/using-jekyll-plugins-with-github-pages/#configuring-jekyll

/me glares at @aron across the internets. :wink: