Sort batches by submitted_at timestamp

Author: andylolz

batch_mailchimp/batches_api.py

@@ -154,6 +154,7 @@ def list(self, refresh=False, **kwargs):
                     self._batches[batch_data["id"]].update(**batch_data)
                 else:
                     self._batches[batch_data["id"]] = Batch(self, **batch_data)
+            self._batches = sorted(self._batches, key=lambda x: x.submitted_at)
         return self._batches
 
     @no_batch