Pytest migration

[asmodehn]

Modifying tests to run independently or as packages, with pytest.

relies on #60

[garethdmm]

This is quite difficult to parse without more explanation. To start can you describe specifically the changes that were needed to get pytest working? Do the same changes work in python 2 as well?

[asmodehn]

I tested locally only on python2, but I based the change on #60 to move forward, and auto test with python3.6 with travis.
Changes were minimal, it will become easy to parse after #60 is merged in the python3 branch.

Unless you want the changes in before #60 ?
I could rebase this branch on master if you prefer, just let me know.

[asmodehn]

logic tests run fine in python2.
extra tests are failing and I haven't checked environment tests.

In python3.6 it seems I hit something similar to https://stackoverflow.com/questions/13194384/instantiate-decimal-class... You can see it there : https://travis-ci.com/garethdmm/gryphon/jobs/222258554
I haven't investigated further yet.

@cclauss did you experience the same thing ? Any clue ?