As described in https://github.com/alshedivat/al-folio/issues/300,
standard Markdown code highlighting doesn't work in the Distill template
because it is clobbered by the Distill "Prism" syntax highlighting. This
PR will allow d-code tags (distill-specific code tags) to function with
the Distill syntax highlighter, but will default `highlight` and
Markdown code blocks to use the Jekyll/Rouge highlighter.
This PR also removes overrides.js, which is currently broken because
jquery isn't loaded.
10d007a98c