Lighting items when uses more 2 level depth

Upgrade `isChildActive` method for lighting items when uses more 2 level depth.

Example: 
```php
echo NavX::widget([
	'options' => ['class' => 'navbar-nav'],
    'encodeLabels' => false,
    'activateParents' => true,
    'items' => [
    	[
        	'label' => Icon::show('reorder') . Yii::t('app', 'Modules'),
            'items' => [
            	[
                	'label' => Icon::show('image') . Yii::t('app', 'Photos'),
                   	'items' => [
                    	[
                        	'label' => Icon::show('sort-alpha-asc') . Yii::t('app', 'All'),
                            'url' => ['/photos/default/index'],
                        ],
                        [
                            'label' => Icon::show('folder') . Yii::t('app', 'Categories'),
                            'url' => ['/photos/categories/index'],
                        ],
                    ],
                ],
            ],
        ]
    ],
]);
```