Apparently, the filters implementation was doing some sort of strange
caching, where you would need to restart the server in order to
refresh for changes to the markdown content.
We fix this by switching to just calling the render_markdown_path
function from Jinja2.
Fixes#5974.
This isn't very slick, but it should get the main points down,
and it's past time we got something like this up. Definitely
needs in the future another pass at the text, and also some images
(screenshots, etc.) and styling.