Alternate infrastructure for testing event filters

### What was wrong?

Testing event filters sucks. Either we depend on `eth-tester` which *probably/maybe* implements the filter logic correctly, or we use `geth` which results in flaky tests and the bad kind of black-box testing since when things fail we don't really have any good way to know why...

### How can it be fixed?

I recently wrote this: https://github.com/ethereum/cthaeh

The most relevant parts are:

- The SQLAlchemy ORM models:
- https://github.com/ethereum/cthaeh/blob/a3f63b0522d940af37f485ccbeed07666adb465b/cthaeh/models.py
- The filtering logic:
- https://github.com/ethereum/cthaeh/blob/a3f63b0522d940af37f485ccbeed07666adb465b/cthaeh/filter.py

If we were to extract these two bits plus some other *support* code into something stand-alone that is more like a *library* then we should be able to use this for testing our log filter code.