Refactored setup.py.
Refs #3, refs #11 - Introduced tox configuration. Added setup.cfg template (empty).
Refs #3 - 'python setup.py test' runs tox.
Refs #3 - Moved tox stuff after 'constants' in setup.py. Added 'with_tox' option in 'index.html'.
Introduced Tox configuration. Closes #3