Pull in ethereum/tests and test against it

[pinkiebell]

Bounty

We need more tests for the system, at best we use the existing https://github.com/ethereum/tests
and integrate those into our (coverage) pipeline, both for the contracts and the js library.

Deliverables

Much better testing for edge cases and proper tests for all the inner workings.
Maybe we even discover 🐛's

Roles

bounty gardener: name / share
bounty worker: name / share
bounty reviewer: name / share