Python 2.7

[jayvdb]

Python 2.7 should still be achievable

[jayvdb]

https://github.com/EFForg/https-everywhere/tree/master/test/rules/src/https_everywhere_checker and https://github.com/google/sre_yield are not Python 2 compatible. As a result, rule analysis and running the upstream tests wont be possible on Python 2.

#22 is a way to get the testing fully functional on Python 2.