* Added a dedicated tox configuration file, and a Makefile target to run
tests,
* Added circle-ci job to test Python2.6,
* Added Documentation about how to keep Python 2.6 compatibility,
* Fixed non-Python 2.6 code, sadly.
* Added classifiers for Python 2.6 in setup.
closes #6
* Added ``expiration_limit`` argument. Default value is ``0``, so you're only checking for *already expired* files,
* Updated documentation in README.
* Updated docstrings
The data files were downloaded on July 26th 2019.
Also added the bare minimum configuration to build a source package.
Updated the README with copyright mentions and a usage example.