WIP: Add test for transitive dependency.

This test should throw an exception.

The idea is to throw an exception when the transitive `Fhaculty\Graph\Edge\Directed -> Fhaculty\Graph\Set\VerticesAggregate` found

I guess I misunderstand the `getVerticesEdgeTo()` or `getVerticesEdgeFrom()`.

![duplicate-fhaculty graph edge base](https://f.cloud.github.com/assets/371014/1819461/8b95bc5a-7095-11e3-987f-ce629f84cadc.png)