make .parented() work so #each can use it

The problem was we don't currently chain callbacks like rendered and parented when a class and superclass have different implementations.  The plumbing here is all rather arbitrary, considering our inheritance model is not finalized (and we may even do away with it, a la React) and "parented" is at best an undocumented but usable peer to "rendered".

Renamed the "parented" signal from DomRange to Component "notifyParented".

packages/ui/base.js

@@ -298,7 +298,7 @@ _extend(UI.Component, {
 
 // XXX we don't really want this to be a user-visible callback,
 // it's just a particular signal we need from DomRange.
-UI.Component.parented = function () {
+UI.Component.notifyParented = function () {
   var self = this;
   for (var comp = self; comp; comp = comp._super) {
     var events = (comp.hasOwnProperty('_events') && comp._events) || null;
@@ -336,10 +336,26 @@ UI.Component.parented = function () {
     });
   }
 
-  // XXX think about this callback's timing
+  var updatedTemplateInstance = false;
+
+  // XXX this is an undocumented callback
+  if (self.parented) {
+    Deps.nonreactive(function () {
+      if (! updatedTemplateInstance) {
+        updateTemplateInstance(self);
+        updatedTemplateInstance = true;
+      }
+      self.parented.call(self.templateInstance);
+    });
+  }
+
+  // XXX fix this callback's timing
   if (self.rendered) {
     Deps.nonreactive(function () {
-      updateTemplateInstance(self);
+      if (! updatedTemplateInstance) {
+        updateTemplateInstance(self);
+        updatedTemplateInstance = true;
+      }
       self.rendered.call(self.templateInstance);
     });
   }

packages/ui/domrange.js

@@ -114,10 +114,8 @@ var rangeParented = function (range) {
       });
     }
 
-    // XXX is this a real callback?  what about chaining? etc.
-    if (range.component.parented) {
-      range.component.parented();
-    }
+    if (range.component.notifyParented)
+      range.component.notifyParented();
 
     // recurse on member ranges
     var members = range.members;

packages/ui/each.js

@@ -6,8 +6,7 @@ UI.Each = Component.extend({
     this.sequence = this.data;
     this.data = undefined;
   },
-  // xcxc -> parented
-  rendered: function () {
+  parented: function () {
     var self = this.__component__;
 
     var range = self.dom;