Replace calls to django.conf.urls.url with django.urls.path or re_path

[jeromelebleu]

django.urls.path and re_path methods have been added in Django 2.0 and django.conf.urls.url method is deprecated since the 3.1 release.

[markfinger]

Thanks, I'll cut a new major release as I guess this'll break Django 1.x compat.

[markfinger]

Thanks again, I've pushed 2.0.0 to PyPI.