Set repository to the fork with an app.json file

Fixes deploying Jekyll from clone.herokuapp.com, I get this error currently:

![screen shot 2014-08-07 at 3 37 10 pm](https://cloud.githubusercontent.com/assets/66427/3850296/71219532-1e83-11e4-833b-4e1111b6756d.png)

Is this change correct?