Enumerations on Python 2.7 were not always implicitly converted to
integers (depending on the target size). This patch adds a __long__
conversion function (only enabled on 2.7) which fixes this issue.
The attached test case fails without this patch.
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
