Make python 3 compatible

[Permafacture]

Make compatible with python 2 and 3 using __future__ and six if necessary.

[chemsed]

all the code are in python 2?

[Permafacture]

I have only run it with python 2. I don't think there is much if any python 2 specific code in it. One thing I don't know is if the same requirements.txt would work for both.

[chemsed]

Hello, I'm running into some issue importing numpy_ecs when I execute polygons.py. Do you have a clue how can I solve that? I think I can find my solution if you explain to me the purpose of setup.py and requirements.txt.

[Permafacture]

In the same directory as setup.py, do

pip install -r requirements.txt
pip install -e .

The e flag means install it in developer mode, so changes you make are
available next time you import it. Otherwise, pip just copies the files to
it's site-packages directory.

[hemebond]

There is no requirements.txt. I just needed to pip install numpy and pyglet.