fix(delegate): it now works in every which way

Custom property annotations have been very useful, to steer very special
cases.

It's also good that now there is enough infrastructure to deal with
any amount of additional type parameters.

src/rust/dev/mod.rs

@@ -93,7 +93,7 @@ mod tests {
                                       <MemoryStorage as Default>::default(), None);
         let mut hub = YouTube::new(hyper::Client::new(), auth);
         let result = hub.channel_sections().insert()
-                     .delegate(&mut <DefaultDelegate as Default>::default())
+                     .delegate(&mut DefaultDelegate)
                      .doit();
     }
 }