Bump to v4.0.0.

internal/hashSet.js

@@ -0,0 +1,22 @@
+define(['./nativeCreate'], function(nativeCreate) {
+
+  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
+  var undefined;
+
+  /** Used to stand-in for `undefined` hash values. */
+  var HASH_UNDEFINED = '__lodash_hash_undefined__';
+
+  /**
+   * Sets the hash `key` to `value`.
+   *
+   * @private
+   * @param {Object} hash The hash to modify.
+   * @param {string} key The key of the value to set.
+   * @param {*} value The value to set.
+   */
+  function hashSet(hash, key, value) {
+    hash[key] = (nativeCreate && value === undefined) ? HASH_UNDEFINED : value;
+  }
+
+  return hashSet;
+});