add implementation for random wp method

[steve-anunknown]

Implemented the randomized version of the Wp method which is quite popular. I believe it should be part of the available equivalence oracles.

Incorporated the oracle to the test_deterministic.py unit test. Also created a unit test test_rwpmethod_oracle.py similar to the existing ones for w / wp methods.

Finally, exposed the class by adding it to the __init__.py file.

[emuskardin]

@steve-anunknown

I merged it, and renamed bound to num_tests.

More importantly, there was a small bug there that can happen with KV. Namely, it can happen that its intermediate hypothesis (does not apply to final one!) are non-minimal, and then characterization set cannot be computed. So in that case I just substituted characterization set with the input alphabet.