Add 'code-block' directive and Pygments parsers

[stollr]

Hi. I am not very familiar with reST, Sphinx and all these. But somethimes I want to extend the documentation of a project (e.g. Symfony) and this online editor is really great for this task ;-) thanks!

But I am missing the code-block directive and the parsing of different languages like "jinja" for example. Symfony uses it, please look at http://symfony.com/doc/current/contributing/documentation/format.html#syntax-highlighting

I am not sure if Pygments is automatically integrated in Sphinx and for that reason this issue may be obsolete because of #9