sub menus didn't get checked for being active.

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

Updated to avoid full tree traversal.
Also noticed ```activateItems``` didn't do anything so that's been fixed.
Update CHANGELOG.md
Added DI container implementation.
Turn module and application into DI containers.
Fixed test break.
fixed test break.
Added unit tests.
Refactored container.
refactored code to use Instance::ensure()
Implemented conditional validators (see #2406)
Made Theme::basePath optional fixes #2810
reverted deletion of Theme::getPath()
fixed Theme::getPath()
Merge pull request #2811 from dmeroff/theme_enhancements

Made Theme::basePath optional fixes #2810
throw exception when UrlManager is not properly configured in console mode.
Updated Spanish translation
Typo fix
Update yii.php
Merge pull request #2814 from djfly/patch-3

Update yii.php