Bump to v4.0.0.

internal/cloneSet.js

@@ -0,0 +1,16 @@
+define(['./addSetEntry', './arrayReduce', './setToArray'], function(addSetEntry, arrayReduce, setToArray) {
+
+  /**
+   * Creates a clone of `set`.
+   *
+   * @private
+   * @param {Object} set The set to clone.
+   * @returns {Object} Returns the cloned set.
+   */
+  function cloneSet(set) {
+    var Ctor = set.constructor;
+    return arrayReduce(setToArray(set), addSetEntry, new Ctor);
+  }
+
+  return cloneSet;
+});