Math

Hi,

I've added an option to treat $ as math delimiters (the :protect_math option). The text enclosed in $ is exempt from certain transformation (very much like tag text). The output page can use MathJax to render the math (you can see the results here: <http://ratatanek.cz/blog/parameter-estimation-model-checking-biological-systems/>).

There are a few heuristics that attempt to detect whether the $ is indeed a math delimiter. Those that are not are escaped with a backslash (this again helps MathJax to render the dollars literally).

Please let me know what you think.