Make unit tests support python 2 and 3 versions

[futu]

In scope of migration project to Py3 I've noticed that tests/support.py uses print statement and fails on Py3. Using print function in unit test makes test to be able run on 2 and 3 python version.

Add more Python classifiers to setup.py to show to compatibility tools e.g. caniusepython3 that project compatible with Py3.

Build universal bdist_wheel. Project's code can be run on python 2 and 3.

I created a local branch with changes. Code was tested on 2.7 and 3.7 versions.
I can create a PR for that. Does it sound reasonable?

[Ignas]

Yeah, of course - you can create a pull request.