Examine different hashing solutions

[guydav]

I think that while theoretically sound, the universal hashing used seems insufficient in practice - it's being vastly outperformed by the double-hashing scheme implemented, which uses fewer hash functions in practice.

In the future, I would like to play around with an alternative hashing scheme, perhaps:
https://github.com/lemire/StronglyUniversalStringHashing

which is in the arxiv here:
https://arxiv.org/pdf/1202.4961v5.pdf