Nightly built package publishing on testpypi

[maoo]

Configure Travis CI to publish the python-symphony package on https://testpypi.python.org/pypi .

The version of the deployed artifact should include the build number (or ID), for example appending -${buildNumber} at the end of the version; only commits on stable branches should trigger the package publishing, ie master.

PyPi credentials can be managed using Travis CI encrypted variables