Removed six dependency

[MightySCollins]

Django 3 has now removed the six util module but this package already seems to only support higher than Python 3.4 as of version 0.14.x.

[auvipy]

we need to wait for this.

[codingjoe]

@auvipy why do we need to wait and what for? This prevents me from testing Django 3.0a1 against some of my test suites. Would it be ok, to simply try ... except the import and use str for the places where the import fails?

[MightySCollins]

I am happy to change the PR to try ... except the only reason I did not was because according to the README Python 2 has already been dropped.

[codingjoe]

@MightySCollins true, that shouldn't be needed, however we do need to get the test suite for Django 3.0 running, I gave it a shot in #200, but I am out in the woods for a couple days. Be my guest to fix it. Would be great if you get it running 👍