pysha3, which is EOL, is listed as a requirement, but doesn't appear to be used.

Hey friends. How are y'all?

So, `pysha3==1.0.2` is listed as a dependency in the requirements file. As you can see, this project is EOL and no longer supported: https://github.com/tiran/pysha3.

I forked this repo with a mind toward using `hashlib` or `eth_utils` instead of `pysha3`, but it appears that... that's already the case?

A brief foray into the history hasn't illuminated where `pysha3` was used - maybe somebody who is more familiar with the dependencies can chime in?

Here's a simple commit updating a couple of dependencies and yanking `pysha3`, and the tests still pass: #20