Create Python 3 compatibility

[niccokunzmann]

We need to check

division i / j  -> i // j
for c in bytes: ord(...)

maybe the tool 2to3 can do good work for us.

[mdxs]

or use six for supporting both: https://pypi.python.org/pypi/six

[niccokunzmann]

Pull request #7 needs to be reviewed and fixes this issue.