Improved CSS and Markdown Syntax Highlighting

Quickly added a few rules for more consistent highlighting in .css and markdown. Hope the @thinkpixellab folks get around to doing an official version. Stop-gap at this point.

Cheers

Markdown:

![screenshot 2014-04-03 at 11 27 12 am](https://cloud.githubusercontent.com/assets/174269/2605476/b87034ea-bb44-11e3-9e50-4703d6614663.png)

CSS:

![screenshot 2014-04-03 at 11 27 38 am](https://cloud.githubusercontent.com/assets/174269/2605484/cae398b0-bb44-11e3-862d-da948c3a2b48.png)