[WIP] Hash Saga Part 5 (RIPEMD160 support)

Dependent on #121, #123, #124

Adds RIPEMD160 + a long string test generator.

Note that the long string hash test for RIPEMD160 adds a vector in the test. You can verify this vector (for b"a" * 1000000) on the RIPE homepage: http://homes.esat.kuleuven.be/~bosselae/ripemd160.html