This commit adds support for Django 1.9. As the template configuration options
changed with Django 1.8 and versions earlier than 1.8 aren't supported anymore
anyway by upstream, support for them is removed.
To have the Dockerfile still working, this commit also changes its logic so the
dependencies get directly installed via the requirements.txt from PyPI, which
will ensure that always matching versions of all dependencies are present (e.g.
the Django version).
Jeffrey Forman
Daniel Roschka