Add Python3 support

Hey,

It's up to you if you want this, but I added support for Python 3 to this code, since Python 3 is the default on Arch Linux and I wanted to use it with Python 3.

This still maintains compatibility (through #if directives) with Python 2, so there's no loss of functionality.

The maintenance effort of ensuring compatibility is hopefully worth it. I think it's awesome to see more useful modules with Python 2/3 support, and I really hope you agree.

Thanks for reviewing,

Nathan