Add support for writing Latex code in markdown

Hi Tomas,

I added feature to write Latex math in markdown:

- To use inline math mode, just embedded your latex code between `$`: `$ ... $`
- To use block math mode, just start a paragraph with first line `$$$`

In latex generator, it simply printout the raw latex code; In HTML generator, it will generate code:

- For inline math mode: `<span class="math">\( ... \)</span>`
- For block math mode: `<p><span class="math">\[ ... \]</span>`

These are grammar of [mathjax](http://www.mathjax.org/), so you need also add a javascript link in your template:

~~~html
<script type="text/javascript"
  src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script>
~~~

So, when the page is first loaded, all those math is displayed as raw latex code, but after a while, when the javascript is loaded, they will be rendered very pretty.

I created some examples online so you can have them a preview:

- [Using with markdown](http://www.aleacubase.com/cudalab/cudalab_usage-math_formatting_on_markdown.html) and [its raw markdown file](https://raw.github.com/soloman817/CUDALab/master/source/02.CUDALab%20Usage/01.Math%20Formatting%20on%20Markdown.md)
- [Using with F# script](http://www.aleacubase.com/cudalab/cudalab_usage-math_formatting_on_fsharp_script.html) and [its script file](https://github.com/soloman817/CUDALab/blob/master/source/02.CUDALab%20Usage/02.Math%20Formatting%20on%20F%23%20Script.fsx)
- [Using with MetadataFormat](http://www.aleacubase.com/temp/manual/reference/alea_cuda/alea-cuda-utilities-libdeviceex.html) (please check the description of function `__oneover2to32minus1()`

Regards,
Xiang.