add pam authentication backend

README.rst

@@ -227,6 +227,29 @@ How to use Authentic2 as a CAS 1.0 or CAS 2.0 identity provider ?
 4. If needed configure your service to resolve authenticated user with your
    LDAP directory (if user attributes are needed for your service)
 
+
+PAM authentication
+==================
+
+This module is copied from https://bitbucket.org/wnielson/django-pam/ by Weston
+Nielson.
+
+Add 'authentic2.vendor.dpam.backends.PAMBackend' to your
+``settings.py``::
+
+  AUTHENTICATION_BACKENDS = (
+      ...
+      'authentic2.vendor.dpam.backends.PAMBackend',
+      ...
+  )
+
+Now you can login via the system-login credentials.  If the user is
+successfully authenticated but has never logged-in before, a new ``User``
+object is created.  By default this new ``User`` has both ``is_staff`` and
+``is_superuser`` set to ``False``.  You can change this behavior by adding
+``PAM_IS_STAFF=True`` and ``PAM_IS_SUPERUSER`` in your ``settings.py`` file.
+
+
 Roadmap
 =======