Removing pysha3 as a dependency, updating others

[jMyles]

Presently, this is as small and surgical as is fit to pass the test suite.

If the preference is for a broader dependency update, I can do that too.

[derekpierre]

Presumably here as well - https://github.com/ConsenSysMesh/py-eip712-structs/blob/master/setup.py#L14.