Add pygments support

Add the Pygments CSS in the base.html
You can use any Pygments theme - just change the path to the CSS file. For an overview see http://igniteflow.com/pygments/themes/

![pygments_support](https://f.cloud.github.com/assets/4996313/1015124/d5a03876-0bd1-11e3-8514-872bb894827f.png)