fixes bug 1048400 - Upgrade to django-compressor 1.4

@AdrianGaudebert r?
cc @bramwelt

Trevor, I'd ask you to review but at this point Adrian is more familiar with the webapp and how to test it and run it locally. 

I've tested this locally with `DEBUG=False` and first running `./manage.py collectstatic --noinput && ./manage.py compress --engine=jinja2 --force` and it works wonderfully.