Bump to v4.0.0.

internal/cloneMap.js

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