Add support for syntax highlighting

## How to use it

Highlighting code with pygments, one would do something like the following in one's posts:

    {% highlight html %}
    <p>Here's some html</p>
    <% endhighlight %}

Pygments supports highlighting of [a lot of languages](http://pygments.org/docs/lexers/). 

## What it looks like

![Screen Shot 2013-01-06 at 2 38 18 PM](https://f.cloud.github.com/assets/145744/45946/78003d58-5806-11e2-9e09-019331327b3c.png)

## System requirements: 
- python 2.4 or higher
- [pygments](http://pygments.org/)