[Deps] switch to object.assign, and unpin util

Author: ljharb

assert.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var objectAssign = require('object-assign');
+var objectAssign = require('object.assign/polyfill')();
 
 // compare and isBuffer taken from https://github.com/feross/buffer/blob/680e9e5e488f22aac27599a57dc844a6315928dd/index.js
 // original notice:

package.json

@@ -3,8 +3,8 @@
   "description": "The node.js assert module, re-packaged for web browsers.",
   "version": "1.5.0",
   "dependencies": {
-    "object-assign": "^4.1.1",
-    "util": "0.10.3"
+    "object.assign": "^4.1.4",
+    "util": "^0.10.4"
   },
   "devDependencies": {
     "mocha": "~1.21.4",