Register the exception, not the message

- Since getDetail() will introspect the exception to determine whether or not to
  display just the message or also include the stack trace, pass the exception
  in.

Author: weierophinney

src/ZF/ApiProblem/Listener/ApiProblemListener.php

@@ -164,8 +164,7 @@ public function onDispatchError(MvcEvent $e)
             if (0 === $status) {
                 $status = 500;
             }
-            $detail  = $exception->getMessage();
-            $problem = new ApiProblem($status, $detail);
+            $problem = new ApiProblem($status, $exception);
         } else {
             // If it's not an exception, do not know what to do.
             return;