Add proper Python 3 compatibility

[ubruhin]

Currently the client has set use_2to3 = True in its setup.py to get compatibility with Python 3. But unfortunately this automatic conversion doesn't work always properly and is very annoying to debug as the code of an installed package is not the same as the original code of the repository. In #57 I already needed to implement a hacky workaround to prevent 2to3 from performing an illegal conversion.

It would be nice to remove use_2to3 = True from setup.py and properly implement Python 3 compatibility in all files. Of course while still keeping Python 2 compatibility, as Funq only works with Python 2 on Windows.

[dbrgn]

as Funq only works with Python 2 on Windows

winappdbg seems pretty much dead (last release in 2013). Maybe there's a package that could replace it?

[dbrgn]

Oh, wait, there's some activity here apparently! https://github.com/MarioVilas/winappdbg

Edit: However: https://github.com/MarioVilas/winappdbg/issues/63

[ubruhin]

Setuptools removed support for use_2to3 (changelog) so Funq can no longer be installed on recent systems :sob:

I created #74 to finally get Funq working with Python 3 on Windows. So I'd say there's no reason anymore to keep supporting Python 2. Removing Python 2 compatibility makes it easier to get rid of use_2to3 (just completely migrate to Python 3). Then Funq will work with recent setuptools versions.

@parkouss Would you agree with removing Python 2 support completely?