[1.7.x] Updated startproject MIDDLEWARE_CLASSES in docs.

Backport of ad31bc0 from master

docs/topics/http/middleware.txt

@@ -32,6 +32,7 @@ here's the default value created by :djadmin:`django-admin.py startproject
         'django.middleware.common.CommonMiddleware',
         'django.middleware.csrf.CsrfViewMiddleware',
         'django.contrib.auth.middleware.AuthenticationMiddleware',
+        'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
         'django.contrib.messages.middleware.MessageMiddleware',
         'django.middleware.clickjacking.XFrameOptionsMiddleware',
     )