Changed the Documentation nav link's url path

Old URL path would direct to craftyjs.com/api/api/ if clicked while on the Documentation page already, which was resulting in a 404.

New path properly goes to the Documentation page if already on it, as well as the other pages. 

Please see the url in the status bar of the attached image for clarification.
![Screen Shot 2013-02-04 at 4 17 30 AM](https://f.cloud.github.com/assets/92724/123480/f62d3328-6ec4-11e2-8775-347860149614.png)
![Screen Shot 2013-02-04 at 4 19 00 AM](https://f.cloud.github.com/assets/92724/123482/18ac8606-6ec5-11e2-9268-721b2e323c0c.png)