Make the code compatible with new version of django

Branch: pierre-sassoulas/django_hreflang:update_django_version

Branch: mverleg/django_hreflang:master

Merged

#2 · Created 2018-03-26 · Last updated 2018-03-29

Merged pull request

Merged in pierre-sassoulas/django_hreflang/update_django_version (pull request #2)

7955355·Author: Pierre Sassoulas·Closed by: Mark V·2018-03-27

When using django 2.0.3 I discovered some problems :

Change in django import causing this error: No module named 'django.core.urlresolvers' See https://stackoverflow.com/questions/43139081/

Also a problem with MiddleWareMixin : TypeError: object() takes no parameters See https://stackoverflow.com/questions/42232606/

Added auto safe escaping of string in order to not have to use autoescape off around {% hreflang_tags %}/

I added some precisions regarding the compatibility with django version. Maybe it could be encoded in the setup.py ?