Add documentation on the hash algorithm

[GoogleCodeExporter]

As far as I can see, there's no documentation on how the thing actually works. 
The source code is rather complex. Are there any Google-internal docs? If so, 
is there any chance of releasing them? Implementations in different languages 
would be so much easier to write...

Original issue reported on code.google.com by JanecekP...@seznam.cz on 26 Jan 2015 at 1:14

[rurban]

Well, it's a tiny improvement over CityHash. Other than that it's an ordinary 3 step hash, as all the others also, with some shuffling and a murmur-like sbox in the middle. It adds faster native crc32 intrinsics and is much better than murmur. A pure C version is here: https://github.com/uxcn/farmhash-c