Doc stylesheet

Haven't worked out how to hook this up yet - probably just append to codo.css using grunt or something. Anyway, to get this under source control here's a PR ;)

To use this, append to codo.css ... it may actually be easier to include this in mozart.io repo instead and append with grunt when the site gets run up. Not clear enough on the workflow yet.

Preview:
![image](https://f.cloud.github.com/assets/4961726/1198141/d3c87ebe-24ef-11e3-86a0-c73f698f1666.png)