Fixed math and emphasis detection by reverting to previous regex. (Leaving marked.js as a parameter for now, though. Still thinking about the best way to do detection.)
Syntax highlighting call was unnecessarily complex. Fixing that removed the need for a document parameter to markdownRender.
Isolated html-to-text logic into module and now using that for forgot-to-render MD detection. Still need to get rid of now-duplicate html-to-text code used when rendering.