Add support for uint8_t * strings

[siara-cc]

Hi, Thank you for making this library! Great work!!

I made some modifications to support binary strings for my case and I thought could be useful to others too. However, no pressure on this - feel free to reject the PR if you don't feel like adding such feature.

If there is some way to improve the positivity rate please let me know. Although I have not done specific tests, RocksDB's bloom filter seems to achieve better rate with 10 bits per key, although their implementation is quite sophisticated.