adding csx support

- [x] detect file extension and highlight like it were a C# file
- [x] do something fancy with the #load and #r entries

### Preview

![screen shot 2014-02-27 at 10 00 02 pm](https://f.cloud.github.com/assets/359239/2281518/9fb02972-9f9e-11e3-89f6-1fa8df63ca93.png)

I'll figure out how to style it tomorrow - open to suggestions/improvements over what's currently there...

Resolves #1