Add python3 import __future__
Change xrange to range for python3 compatibility
Make long int usage Py3 compatible

In particular Python ints are promoted to longs automatically when
needed, so trailing L's are almost never needed.
Replace iterkeys with keys for python3 compatibility
Fix broken tab using indentation

Might have broken the code, but it didn't have a unittest so I don't
care.
Make (un)hexlify() usage py3 compatible
Fix chr/ord related py3 incompatibilities
Add python3 invocation of unittests
Merge pull request #10 from petertodd/python3-fixes

Python3 fixes