Add an iterate() api call, that handles both Model and Collection.

@@ -57,6 +57,13 @@ define(function(require) {
                     }
                 }
             },
+            iterate: function iterate(obj, callback, context) {
+                if (obj instanceof Model) {
+                    obj.each(callback, context);
+                } else if (obj instanceof Collection) {
+                    obj.each(callback, context);
+                }
+            },
         };
     })(Backbone.Model, Backbone.Collection, 'add remove reset sort');
     return adapter;