Add "clean" and "clobber" Makefile targets
Basic python3 compatibility, via the 'six' module.
Merge pull request #3 from mozilla/rfk/py3

Basic python3 compatibility, via the 'six' module.
Trade auth code and verify token
Timestamp header is not returned by OAuth server
First bits of documentation
Check OAuth scope if provided
Python 3 compatibility
Python 2.6 compatibility