More improvements in support of moving training manual to wiki

- The Django-wiki doesn't seem to support code nested in a list, but Remark.js does. This patch looks for code blocks immediately following a list item and does the right thing to nest the code in the list for the slide show.
- I also added basic support for using Reveal.js (http://lab.hakim.se/reveal-js) as an alternative to Remark.js, I would like to have both as an option, but Reveal is lacking some of the control that Remark allows.