add note about aot upgraded comps and lifecycle hooks

Author: filipesilva

public/docs/ts/latest/guide/upgrade.jade

@@ -798,6 +798,12 @@ figure
 :marked
   And that's all we need to get the full benefit of AoT for Angular 2 apps!
 
+.alert.is-helpful
+  :marked
+    The AoT metadata collector will not detect lifecycle hook methods on a parent class' prototype,
+    so in order for upgraded components to work we needs to implement the lifecycle hooks 
+    on the upgraded component class and forward them to the `UpgradeComponent` parent.  
+
 :marked
   ## Dividing routes between Angular 1 and 2