Added `Next`-Link in setup and basic propel docs

Now you don't have to scroll back to top every time
when you finished reading the page.

![bildschirmfoto 2014-10-05 um 01 42 12](https://cloud.githubusercontent.com/assets/2072185/4517131/1a75dade-4c20-11e4-8f6c-884fc77d0cce.png)