Datasketch

* Added Asynchronous MinHash LSH module. Thanks aastafiev!
* Added ability to set the base name in storage config. Base name is used as the
prefix for generating keys in the underlying storage (e.g., Redis).
This change allows client to "reconnect" to an existing LSH index in the storage through its base name.

Fix a bug with UnorderedStorage.get_many (56)

* Fix issue 35
* Test cases for checking consistency of hash value length in LSH.

Thanks vmarkovtsev

* Introduced a Redis storage layer for MinHash LSH. Thanks to ae-foster
* Added `__hash__` method for Lean MinHash.

* Added a slightly simplified version of [LSH Ensemble](http://www.vldb.org/pvldb/vol9/p1185-zhu.pdf) that supports containment search with MinHash data sketches.
* An introduction on containment [link](https://ekzhu.github.io/datasketch/lshensemble.html#containment).
* Update documentations