Update example project for Django>2 (#391)

example/cheeseshop/settings.py

@@ -47,7 +47,7 @@ INSTALLED_APPS = (
     'constance.backends.database',
 )
 
-MIDDLEWARE_CLASSES = (
+MIDDLEWARE = (
     'django.middleware.common.CommonMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',

example/cheeseshop/urls.py

@@ -1,11 +1,11 @@
-from django.conf.urls import include, url
+from django.conf.urls import url
 from django.contrib.staticfiles.urls import staticfiles_urlpatterns
 from django.contrib import admin
 from django.conf import settings
 admin.autodiscover()
 
 urlpatterns = [
-    url(r'^admin/', include(admin.site.urls)),
+    url(r'^admin/', admin.site.urls),
 ]
 
 if settings.DEBUG:

example/requirements.txt

@@ -1,2 +1,2 @@
-Django
-python-memcached
+Django>=2.2
+python-memcached