Cython bindings for MurmurHash2.

MurmurHash is a non-cryptographic hash function suitable for general hash-based
lookup. It was created by Austin Appleby in 2008 and, as of 8 January 2016,
is hosted on GitHub along with its test suite named SMHasher. It also exists in
a number of variants, all of which have been released into the public domain.
The name comes from two basic operations, multiply (MU) and rotate (R), used in
its inner loop.