Add a management command to clean up stale OpenID associations and

nonces.

django_openid_auth/management/commands/openid_cleanup.py

+from django.core.management.base import NoArgsCommand
+
+from django_openid_auth.store import DjangoOpenIDStore
+
+
+class Command(NoArgsCommand):
+    help = 'Clean up stale OpenID associations and nonces'
+
+    def handle_noargs(self, **options):
+        store = DjangoOpenIDStore()
+        store.cleanup()