#382 fix asciidoc math equations

[Sebastian Kuzminsky]

We currently hand-generate pngs and post-process the html files to to insert them, there must be a better way.

[Sebastian Kuzminsky]

This is the current process for updating a Latex math image:

1. Uncommented the relevant latex part of the asciidoc .txt file.
2. Run 'make doc' to generate the html file with the latex source in a pass-through block.
3. Run html-latex-images on the html file to generate the updated .png files.
4. Overwrite the .png in git with the regenerated one from the script and commit.