A flake8 configuration is included in setup.cfg and the checks are
executed automatically on Travis:
* Ensures a consistent PEP8 code style
* Does basic linting to prevent possible bugs
Use simple asserts and pytest's powerful introspection to make testing
simpler. This merges the old .py/.ref file pairs into simple .py files
where the expected values are right next to the code being tested.
This commit does not touch the C++ part of the code and replicates the
Python tests exactly like the old .ref-file-based approach.
