Proposal: Adopt the six library, or drop Python 2 support about zoomus

[prschmid]

Since Python 2.7 is still supported until the end of 2019, let's keep it supported at least until then. As such, using the six library is the way we'd want to go to make sure we don't leave anyone high and dry.

[tarkatronic]

@prschmid I saw that you dropped Python 2 from the docs and testing grid. With that, I would love to put in a bit of additional work to rip out any Python 2 shims which exist!

[prschmid]

Thanks for your willingness to put in that effort!

Yes, I indeed dropped the official support for it since 2.7 EOL was in January. That being said, I'd like to keep unofficial support for it for a bit longer since I have no idea the environment that people are running things in. Having the (unofficial) python 2.7 support isn't a great overhead at this moment, so, let's keep it around a bit longer.