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
fixed refences
fixed another reference
more reference fixes
Added asElapsedTime function
Typo in asElapsedTime description
Call Yii::t everytime instead of passing a template variable
Typo
[doc]Composer is not a package manager.

It is a issue i found when I translate it.
> Composer is not a package manager, It's a tool for dependency management.

According to their [doc](https://getcomposer.org/doc/00-intro.md)
>Composer is a tool for dependency management in PHP. It allows you to declare the dependent libraries your project needs and it will install them in your project for you.

and 

> **Composer is not a package manager.** Yes, it deals with "packages" or libraries, but it manages > them on a per-project basis, installing them in a directory (e.g. vendor) inside your project. By > default it will never install anything globally. Thus, it is a dependency manager.

So i think, It will be better, if we remain their offical appellation.
Merge pull request #2718 from qiansen1386/patch-2

[doc]Composer is not a package manager.
Update view.php
Update files.php
Update CHANGELOG.md
asElapsedTime can now take DateInterval as parameter
asElapsedTime style improvements
Merge pull request #2719 from klevron/2712

Fix #2712
CS Fix
asElapsedTime can now take a DateInterval string as a parameter