Add code to stackforge/entropy

Because upstream wasn't mentioned when project was created, merge
existing upstream code manually. Current upstream is
https://github.com/pran1990/entropy

Add first draft of script in entropy/entropy.py. Utils used by the package are in entropy/utils.py

Added licenses to py scripts and LICENCE file

Added tox.ini, requirements.txt, and test-requirements.txt to setup
environments for gerrit's jenkins tests

Added sphinx docs in docs/. Instructions to build docs are in docs/README.rst

Change-Id: Ifff7cff38989e8c5509d3ecf4b34485893bfcfdb