#186 play nice with mathjax extension

[Lee Worden]

there's a separate extension for adding MathJax math to wikis that has nothing to do with WW. If someone installed both, they'd presumably get two copies of the mathjax javascript with each page. Should probably do something about that.

[Lee Worden]

http://www.mediawiki.org/wiki/Extension:MathJax.

Also, MediaWiki itself might start using MathJax, and that would be more important to take into account.