winterfell

Addresses #9 . Based on the recent work. The most noticeable features are: 1. We take into account the degree of the extension field when randomizing. 2. We add randomization of the quotient segment polynomials. 3. We add a random code-word to the DEEP composition polynomial as done in the Aurora paper. 4. In addition to salting the vector commitment, we also salt the Fiat-Shamir as is done in the specification of the BCS transform. This is ready for full review but I am putting in draft mode as the current solution for generating randomness for zero-knowledge is not clean. More specifically: 1. For salted Merkle trees, should we also use a PRNG? 2. For the PRNG used in the prover, I am not happy with the way it is currently implemented, I am thinking that it should be sort of optional to have it but I couldn't come up with a good way to do that. There are also some unnecessary allocations but I can remove those once we agree on the general structure.