Conforming to Django 1.6+ special timeout values

Django 1.6+: Explicitly passing in timeout=None will set a non-expiring timeout. Passing in timeout=0 will set-and-expire-immediately the value.

I didn’t know tox. The tox output was so verbose that I can’t tell if my commit passed the tests or not…
Well if we call <code>add("foo", "bar", None)</code> then <code>uwsgi_timeout</code> will be set to 0 and because at the end we call <code>return self.set(key, value, uwsgi_timeout, self._server)</code> the timeout sent to uwsgi will be 0, am I wrong?

Also I’m going to write some tests for add().