[WIP] Locality Sensitive Hashing for approximate nearest neighbor search(GSoC)

Please compare the results with the same query run on a `sklearn.neighbors.NearestNeighbor` instance and add an assertion that the distances returned by `lshf` are greater or equal to the distances returned by the exact NN query.

The other tests would also benefit from comparision with a reference exact NN query using `sklearn.neighbors.NearestNeighbor`.