Fix issues #130 and #131: Support Lua in Python 3 and improve mock signatures

[beamerblvd]

• Uses a Python-3 compatible Lunatic-Python library from PyPi
• Updates the mock Lua script object to not use Python version-specific builtins / behavior
• Updates the mock Lua script to support redis.status_reply and redis.error_reply in Lua scripts
• Updates the mock Lua script to support unicode
• Updates the signatures of the patching functions to support from_url and Mock-specific kwargs
• Updates the Travis build to run Lua tests, and to also test on Python 3.5 and 3.6
• Updates the Lua tests to be Python 3 compatible

[beamerblvd]

Would love to get a review of this. Currently monkey-patching it in our project, but would prefer to use it unpatched. :-)

[ushuz]

Python 2 should be the special case here. In future, when Python 4 gets released, this if will fallback to the logics for Python 2, which will definitely be incompatible with Python 4.