added caster for std::reference_wrapper (fixes #171)
diff --git a/example/issues.ref b/example/issues.ref
index 55cbdda..74b34c2 100644
--- a/example/issues.ref
+++ b/example/issues.ref
@@ -2,3 +2,4 @@
 c
 Failed as expected: Tried to call pure virtual function "dispatch"
 Yay..
+[Placeholder[1], Placeholder[2], Placeholder[2]]