Bump to v4.0.0.

internal/initCloneObject.js

@@ -1,3 +1,6 @@
+var baseCreate = require('./baseCreate'),
+    isFunction = require('../isFunction');
+
 /**
  * Initializes an object clone.
  *
@@ -7,10 +10,7 @@
  */
 function initCloneObject(object) {
   var Ctor = object.constructor;
-  if (!(typeof Ctor == 'function' && Ctor instanceof Ctor)) {
-    Ctor = Object;
-  }
-  return new Ctor;
+  return baseCreate(isFunction(Ctor) ? Ctor.prototype : undefined);
 }
 
 module.exports = initCloneObject;