Create a script to check any pip installation regressions

We need to be strong against any pip deployment/installation regressions. The idea is to:

• setup a local PyPi server;
• run python setup.py sdist upload on that server.

Then, on each and every platforms (as of now: GNU/Linux, macOS and Windows), do:

• setup a fresh virtualenv;
• run pip install nuxeo-drive from the custom server;
• check that the Drive module works:

  % python
  >>> import nxdrive
  >>> nxdrive.__path__
  ...  # <- it must be inside the virtualenv