Make code Python 3 compatible

[dan-blanchard]

Most of the changes here were created by python-modernize. The gnarlier bytearray-related changes in blowfish.py had to be added manually because that script doesn't know how to handle that stuff.

The setup.py package_dir change was necessary to get pip install -e or python setup.py develop working.

I haven't gotten a chance to test everything with this yet, but I figured it was a quick step in the right direction.

[gaubert]

@dan-blanchard Ok thanks. I need to test it in the coming days and reworke some parts as I can see already.

[mrjcleaver]

@gaubert - did you ever come back to this?