Allow to parameterize seed value as in original murmur3 implementation

[mbyczkowski]

When I was implementing this change, I missed that similar work has been done already (#9 and #10), but I figured it's worth sharing.

• added seed to every constructor (32-, 64- and 128-bit) as well as Sum32, Sum64 and Sum128
• made sure that non-zero seeds are also tested for correctness (used other ref implementations to make sure that seeded outputs are correct and added them in test file)
• my fork has been running in production already 🙂

Obvious drawback is the API breakage of this lib, so maybe the way to go would be to tag the lib and start versioning (e.g. 0.1 for current, and 0.2 for this PR and up)?

[spaolacci]

Thanks for the PR. I had roughly equivalent stahed patch that I uploaded this morning in 4ec5a0f56d4fc178129a8433576bf6f2fe672a9e. The API is extended (not altered) with seed aware constructors and top-level accessors.

It obiously conflicted your patch set, but I'd like to have at through since there's a few well deserved nitpicking, and I also find your seed slot location more ingenious than mine.

I can cherry pick those extra changes manually, it's up to you.

Thanks.

[mbyczkowski]

Extending the API was probably the right move. I have rebased my PR based on your changes and preserved the stuff the I believe you wanted to keep. Lemme know what you think!

[spaolacci]

All merged. Thanks!