Fixed deprecation warning in middleware.py for django 2.0

[Naddiseo]

Update for django 2.0

Importing from django.core.urlresolvers is deprecated in favor of django.urls.

[zetaab]

can this be merged, currently django debug panel does not work in django 2.0. With this fix I got it working

[SamuelMS]

@recamshak +1 on merge request.

[picturedots]

@Naddiseo line 11 needs to be removed for this to work I think

[aymanbagabas]

Please merge this! Breaks in Django 3.0.

[duduklein]

In django 3.0, the render_to_response in views.py also breaks the installation. it should be changed to render only : https://stackoverflow.com/questions/55911435/django-importerror-cannot-import-name-render-to-response-from-django-shortcu