moved mutex back from extensions.

extensions/mutex/LICENSE.md

-The Yii framework is free software. It is released under the terms of
-the following BSD License.
-
-Copyright © 2008-2013 by Yii Software LLC (http://www.yiisoft.com)
-All rights reserved.
-
-Redistribution and use in source and binary forms, with or without
-modification, are permitted provided that the following conditions
-are met:
-
- * Redistributions of source code must retain the above copyright
-   notice, this list of conditions and the following disclaimer.
- * Redistributions in binary form must reproduce the above copyright
-   notice, this list of conditions and the following disclaimer in
-   the documentation and/or other materials provided with the
-   distribution.
- * Neither the name of Yii Software LLC nor the names of its
-   contributors may be used to endorse or promote products derived
-   from this software without specific prior written permission.
-
-THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
-FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
-COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
-INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
-BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
-CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
-LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
-ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
-POSSIBILITY OF SUCH DAMAGE.

extensions/mutex/README.md

-Yii 2.0 Public Preview - Mutex Extension
-========================================
-
-Thank you for choosing Yii - a high-performance component-based PHP framework.
-
-If you are looking for a production-ready PHP framework, please use
-[Yii v1.1](https://github.com/yiisoft/yii).
-
-Yii 2.0 is still under heavy development. We may make significant changes
-without prior notices. **Yii 2.0 is not ready for production use yet.**
-
-[![Build Status](https://secure.travis-ci.org/yiisoft/yii2.png)](http://travis-ci.org/yiisoft/yii2)
-
-This is the yii2-mutex extension.
-
-
-Installation
-------------
-
-The prefered way to install this extension is through [composer](http://getcomposer.org/download/).
-
-Either run
-```
-php composer.phar require yiisoft/yii2-mutex "*"
-```
-
-or add
-```
-"yiisoft/yii2-mutex": "*"
-```
-to the require section of your composer.json.
-
-
-*Note: You might have to run `php composer.phar selfupdate`*
-
-
-Usage & Documentation
----------------------
-
-This component can be used to perform actions similar to the concept of [mutual exclusion](http://en.wikipedia.org/wiki/Mutual_exclusion).
-
-For concrete examples and advanced usage refer to the yii guide.

extensions/mutex/composer.json

-{
-	"name": "yiisoft/yii2-mutex",
-	"description": "Mutual exclusion extension for the Yii framework",
-	"keywords": ["yii", "mutex"],
-	"type": "yii2-extension",
-	"license": "BSD-3-Clause",
-	"support": {
-		"issues": "https://github.com/yiisoft/yii2/issues?state=open",
-		"forum": "http://www.yiiframework.com/forum/",
-		"wiki": "http://www.yiiframework.com/wiki/",
-		"irc": "irc://irc.freenode.net/yii",
-		"source": "https://github.com/yiisoft/yii2"
-	},
-	"authors": [
-		{
-			"name": "resurtm",
-			"email": "resurtm@gmail.com"
-		}
-	],
-	"minimum-stability": "dev",
-	"require": {
-		"yiisoft/yii2": "*"
-	},
-	"autoload": {
-		"psr-0": { "yii\\mutex\\": "" }
-	}
-}