added gunicorn to requirements

git-svn-id: https://svn.eionet.europa.eu/repositories/Python/flis.live_catalogue@134 60810c31-268d-49e0-9aa7-0fbff4fae3ae
added gunicorn to INSTALLED_APPS in settings.py
Merge branch 'master' of github.com:eaudeweb/flis.live_catalogue