Add support for stable/ussuri branch Change-Id: I24fd7eac29d034a44499210fa9751044eabcecf5
* Updated 'test-requirements.txt', 'tox.ini' with relevant 'stable/stein' branch libraries. * Added zuul jobs w.r.t. 'stable/stein' release. * Used 'coverage' library for coverage. * Added 'python3' as basepython for pep8, venv, coverage. * Added 'doc/requirements.txt' file for pep8. Change-Id: I5ca248f31d1b6f2afaf484ce19fcf0e96f35119f
enables the ability of unit testing and the Horizon dependency Change-Id: I880eec30ad032e2cfe02ab9303a2a8b00904fc70