move transformers over to using ast-types when constructing new nodes

lib/6to5/transformers/property-method-assignment.js

@@ -1,4 +1,5 @@
 var util = require("../util");
+var b    = require("ast-types").builders;
 var _    = require("lodash");
 
 exports.Property = function (node) {
@@ -6,9 +7,6 @@ exports.Property = function (node) {
 };
 
 exports.ObjectExpression = function (node) {
-  //if (node.ignorePropertyMethods) return;
-  //node.ignorePropertyMethods = true;
-
   var mutatorMap = {};
 
   node.properties = node.properties.filter(function (prop) {
@@ -24,9 +22,6 @@ exports.ObjectExpression = function (node) {
 
   return util.template("object-define-properties-closure", {
     OBJECT: node,
-    CONTENT: util.buildDefineProperties(mutatorMap, {
-      type: "Identifier",
-      name: "obj"
-    }).expression
+    CONTENT: util.buildDefineProperties(mutatorMap, b.identifier("obj")).expression
   });
 };