Remove references to _.

isUndefined.js

@@ -3,16 +3,15 @@
  *
  * @static
  * @since 0.1.0
- * @memberOf _
  * @category Lang
  * @param {*} value The value to check.
  * @returns {boolean} Returns `true` if `value` is `undefined`, else `false`.
  * @example
  *
- * _.isUndefined(void 0);
+ * isUndefined(void 0);
  * // => true
  *
- * _.isUndefined(null);
+ * isUndefined(null);
  * // => false
  */
 function isUndefined(value) {