Figure out a better way to add classes to specific elements, e.g. HTML tables

[gonX]

While working on #158 (especially be008ef), I noticed that a lot of elements need to have the same classes attached to them. We already kind of "fix" this with JavaScript, but unsurprisingly this results in inconsistent styling for noscript users.

I think the best way to work around this is by extending the current Markdown parser we use, since it does not seem like they have any configuration options that can help with assigning HTML/CSS classes to specific elements.