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

However, your error in the example alerted me to an unhandled case: where `candidates` is empty here it is incorrectly typed (`array([], dtype=float64)`) and this line raises:
```
IndexError: arrays used as indices must be of integer (or boolean) type
```
Please fix the type where you generate `candidates`.