Django 1.7 SimpleAdminConfig use import error fix

From Django 1.7 release notes: django.contrib.admin will now automatically perform autodiscovery of admin modules in installed applications. To prevent it, change your INSTALLED_APPS to contain 'django.contrib.admin.apps.SimpleAdminConfig' instead of 'django.contrib.admin'.

So using default admin app causes ```autocomplete_light.exceptions.AutocompleteNotRegistered (registry is empty)``` error.
Temporary workaround is to use SimpleAdminConfig, but it seems like current behaviour must be changed from one described in docs: http://django-autocomplete-light.readthedocs.org/en/latest/install.html#call-autocomplete-light-autodiscover-before-admin-autodiscover