please add DELTA-DEBUG

Please add DELTA-DEBUG, an implementation of the delta debugging algorithm from the following.

```
 Zeller, Andreas, and Ralf Hildebrandt. "Simplifying and isolating
 failure-inducing input." Software Engineering, IEEE Transactions
 on 28.2 (2002): 183-200.
```

Authors: Eric Schulte
License: GPLV3
Code: https://github.com/eschulte/delta-debug
Documentation: http://eschulte.github.io/graph/
