Add Python 3 support

- use python-requests over pycurl
- generic changes to support python3
- fix tests to support python3
- add *requirements.txt files to handle dependencies
Make things hacking friendly

- added common dev envirionment ignores
- added scripts to help developers create/activate virtualenvs for
  development and testing
- added run-tests script to help run tests across python versions
- updated HACKING file