added constructors for MinHasher and subclasses that allow the number of hashes and number of bands to be input, instead of relying on these being computed from a threshold. motivation: we had a need to guarantee the exact bytes in the hashes for backwards compatibility with previously generated and stored hashes.
changed MinHasher to be monoid on MinHashSignature
per oscar's suggestion public methods now all deal with MinHashSignatures instead of byte arrays
Merge pull request #144 from tresata/feature/hasher-kk

added constructors for MinHasher and subclasses that allow the number of...