In short, a markdown language that feels like GitHub Markdown + LaTeX + CSS
Shameless plug: I have been looking at markdown + TeX for a while.
I currently use https://stackedit.io to write posts. It is a really nice editor for markdown + TeX and also supports exporting to static HTML.
To generate my blog (https://rubenvannieuwpoort.nl) I initially used Jekyll, which has some support for TeX but was rather slow; It takes minutes to generate a very simple site, and if I remember correctly the math was not rendered statically. I now have made my own static site generator (https://github.com/rubenvannieuwpoort/static-site-generator). It consists of some (hopefully simple to understand) bash and node.js scripts, and should be relatively easy to adapt.