Fix display of inline and block code

The pygments.css file wasn't actually highlighting the code due to its strange selectors, so I replaced it with one I generated with `pygmentize -S friendly -f html`. I also added some CSS so that code blocks have a light grey background and so inline code is monospaced.

This is what it looks like:
![codeexample](https://f.cloud.github.com/assets/1570381/608211/22fe87e8-cd58-11e2-90d2-c15ebb5c67a2.png)