Added RoofedForest trees.

Could still be improved a lot.

![2014-07-30_15 56 53](https://cloud.githubusercontent.com/assets/1160867/3749985/628a4494-17f1-11e4-96c8-39422f086023.png)
Could you explain this comment? Parser failed somewhere at: loop 'i' minus two multiply (what?) times