Updated to avoid full tree traversal.
Also noticed ```activateItems``` didn't do anything so that's been fixed.

Based off the method in ```Menu.php``` I've updated ```Nav``` so it will check if sub menus are active or not.

We are now maintaining a fork of pjax:
https://github.com/yiisoft/jquery-pjax

apps code style fixes

* 'master' of github.com:yiisoft/yii2: (40 commits)
  Fixes #2624: Html::textArea() should respect "name" option.
  Removed unused "use" statements
  Changed "and" to "&&"
  Used ternary operator instead of "or" for constant definition
  Removed unused variables
  Removed executable flag from asset files
  Changelog for #2607
  Added note about overriding asset bundles according to #2556
  Added some documentation to new pjax attribute
  Add unit tests
  typo fix.
  Update MessageController.php
  Update MessageController.php
  add findAndModify() method to the Collection class
  Add an option to ignore pjax request on some links.
  fix code style php5.4 syntax
  Inline control structures are not allowed
  fix code style
  fix code style
  fix typo double `;`, `Each PHP statement must be on a line by itself`
  ...

fixes #2623

enchansment of db message source

add findAndModify() method to the Collection class

Add an option to ignore pjax request on some links.

Code style fix