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).
To improve the code quality of binder, this commit adds support for continuous
integration by using Travis CI (https://travis-ci.org/).
This will ensure that every commit and every pull request will trigger test
runs of the tests included in binder, helping to avoid code with broken tests.
Daniel Roschka