Port section heading information to Markdown render

[matthewfeickert]

As @bnachman mentioned in PR #35

Each heading has a small bit of explanation. This appears in the .tex and .pdf versions, but not the markdown (but only because I did not have enough time to make that happen - we can revisit that in the future).

These very nice summaries that Ben has added to the TeX source would be nice to additionally get propagated into the Markdown output as well as the PDF.

[bnachman]

Thank you for opening this @matthewfeickert ! The PDF should already have these because it is in the .tex and properly compiles. The reason it is not in the markdown is simply because it is cleanest to have the explanations after the citations in the .tex, but we want them to come before the citations in the markdown. This will require a little bit of python coding that is not hard, but something that should be done eventually. I already have an if statement in the code that catches all of the explanations but it currently doesn't write anything because it would be in the wrong location (after the citations).