Fixes #22 RestRefundRequest::sendData doesn't set response data as array

Author: Swahjak

src/Message/RestRefundRequest.php

@@ -72,7 +72,7 @@ public function sendData($data)
 
         $this->response = new RestRefundResponse(
             $this,
-            $httpResponse
+            $httpResponse->json()
         );
 
         return $this->response;