I think this should be renamed, as it doesn't actually return a set of edges (perhaps #48 will clarify the concept of a set of edges). This returns a multi-dimensional-array of edges as a result of the computation (see above), so I'm not quite sure *how* to name it.

This is somewhat related to the above comment, but I think an additional `getEdges()` that actually only returns the unique set of edges present in all shortest paths could be provided. It's primary use would probably be graph drawing, so I think providing an additional `createGraph()` also makes sense. It should create a clone of the input graph, but remove all edges not present on either of the shortest paths (see `Algorithm\ShortestPath\Base::createGraph()`).