Fixed #23437 -- Documented required update of WSGI scripts for 1.7.

Otherwise, you will hit an ``AppRegistryNotReady`` exception.

WSGI scripts

~~~~~~~~~~~~

Until Django 1.3, the recommended way to create a WSGI application was::

    import django.core.handlers.wsgi

    application = django.core.handlers.wsgi.WSGIHandler()

In Django 1.4, support for WSGI was improved and the API changed to::

    from django.core.wsgi import get_wsgi_application

    application = get_wsgi_application()

If you're still using the former style in your WSGI script, you need to

upgrade to the latter, or you will hit an ``AppRegistryNotReady`` exception.

App registry consistency

^^^^^^^^^^^^^^^^^^^^^^^^