Raise HTTP errors when calling post_multi()

This allows us to catch more errors that can occour when transferring
data to Setra.

setra_client/client.py

@@ -206,7 +206,8 @@ class SetraClient(object):
         headers = {'Content-Type': 'application/json'}
         response = self.post(url,
                              data=multidata.json(),
-                             headers=headers)
+                             headers=headers,
+                             return_response=False)
         return response