Update dependencies in tox to avoid version conflicts.
Hardcode version for Python3 compatibility.

No execfile support.
Make imports Python 3 compatible.
Don't test for unicode.
Fix basestring for Python3 compatibility.
Don't test for exception.message if not available.
Fix Python3 getting string instead of bytes in SignedRequest.
Make signed request tests pass on Python 3.
Pass exception object to HTTPError instead of message only.
Decode bytes before parsing json.
Update example in README.
Merge pull request #89 from riklaunim/master

Python 3.3 compatibility