Readme redesign (#13682)

* Redesigned readme [skip ci]

* Them → Us

* Clarified reasonable defaults part

* Update README.md

README.md

@@ -1,12 +1,13 @@
-Yii PHP Framework Version 2
-===========================
+<p align="center">
+    <a href="http://www.yiiframework.com/" target="_blank">
+        <img src="http://static.yiiframework.com/files/logo/yii.png" width="400" alt="Yii Framework" />
+    </a>
+</p>
 
-Thank you for choosing Yii 2 - a modern PHP framework designed for professional Web development.
-
-Yii 2 is a complete rewrite of its previous version Yii 1.1 which is one of the most popular PHP frameworks.
-Yii 2 inherits the main spirit behind Yii for being simple, fast and highly extensible.
-Yii 2 requires PHP 5.4 and embraces the best practices and protocols found in modern Web application development.
+Yii 2 is a modern framework designed to be a solid foundation for your PHP application.
 
+It is fast, secure and efficient and works right out of the box pre-configured with reasonable defaults.
+The framework is easy to adjust to meet your needs, because Yii has been designed to be flexible.
 
 [![Latest Stable Version](https://poser.pugx.org/yiisoft/yii2/v/stable.png)](https://packagist.org/packages/yiisoft/yii2)
 [![Total Downloads](https://poser.pugx.org/yiisoft/yii2/downloads.png)](https://packagist.org/packages/yiisoft/yii2)
@@ -18,49 +19,62 @@ Yii 2 requires PHP 5.4 and embraces the best practices and protocols found in mo
 [![Scrutinizer Quality Score](https://scrutinizer-ci.com/g/yiisoft/yii2/badges/quality-score.png?s=b1074a1ff6d0b214d54fa5ab7abbb90fc092471d)](https://scrutinizer-ci.com/g/yiisoft/yii2/)
 [![Code Climate](https://img.shields.io/codeclimate/github/yiisoft/yii2.svg)](https://codeclimate.com/github/yiisoft/yii2)
 
-DIRECTORY STRUCTURE
--------------------
-
-```
-build/               internally used build tools
-docs/                documentation
-framework/           core framework code
-tests/               tests of the core framework code
-```
-
-
-REQUIREMENTS
+Installation
 ------------
 
-The minimum requirement by Yii is that your Web server supports PHP 5.4.
-
+- The minimum required PHP version of Yii is PHP 5.4.
+- It works best with PHP 7.
+- [Follow the Definitive Guide](http://www.yiiframework.com/doc-2.0/guide-start-installation.html)
+in order to get step by step instructions.
 
-DOCUMENTATION
+Documentation
 -------------
 
-Yii 2.0 has a [Definitive Guide](http://www.yiiframework.com/doc-2.0/guide-index.html) and 
-a [Class Reference](http://www.yiiframework.com/doc-2.0/index.html) which cover every detail of Yii.
-
-There is also a [PDF version](http://stuff.cebe.cc/yii2-guide.en.pdf) of the Definitive Guide
+- A [Definitive Guide](http://www.yiiframework.com/doc-2.0/guide-index.html) and 
+a [Class Reference](http://www.yiiframework.com/doc-2.0/index.html) cover every detail
+of the framework.
+- There is a [PDF version](http://stuff.cebe.cc/yii2-guide.en.pdf) of the Definitive Guide
 and a [Definitive Guide Mirror](http://stuff.cebe.cc/yii2docs/) which is updated every 15 minutes.
+- For Yii 1.1 users, there is [Upgrading from Yii 1.1](docs/guide/intro-upgrade-from-v1.md)
+to get an idea of what has changed in 2.0.
 
-For 1.1 users, you may refer to [Upgrading from Yii 1.1](docs/guide/intro-upgrade-from-v1.md)
-to have a general idea of what has changed in 2.0.
+Community
+---------
 
+- Participate in [discussions at forums](http://www.yiiframework.com/forum/).
+- [Chat in IRC](http://www.yiiframework.com/chat/).
+- Follow us on [Facebook](https://www.facebook.com/groups/yiitalk/), [Twitter](https://twitter.com/yiiframework)
+and [GitHub](https://github.com/yiisoft/yii2).
 
-HOW TO PARTICIPATE
-------------------
+Contributing
+------------
 
-### Your participation to Yii 2 development is very welcome!
+The framework is Open Source [powered by an excellent community](https://github.com/yiisoft/yii2/graphs/contributors).
 
-You may participate in the following ways:
+You may join us and:
 
 - [Report an issue](docs/internals/report-an-issue.md)
 - [Translate documentation or messages](docs/internals/translation-workflow.md)
 - [Give us feedback or start a design discussion](http://www.yiiframework.com/forum/index.php/forum/42-general-discussions-for-yii-20/)
 - [Contribute to the core code or fix bugs](docs/internals/git-workflow.md)
 
-### Acknowledging or citing Yii 2
+### Reporting Secirity issues
+
+Please refer to a [special page at the website](http://www.yiiframework.com/security/)
+describing proper workflow for security issue reports.
+
+### Directory Structure
+
+```
+build/               internally used build tools
+docs/                documentation
+framework/           core framework code
+tests/               tests of the core framework code
+```
+
+### Spreading the Word
+
+Acknowledging or citing Yii 2 is as important as direct contributions.
 
 **In presentations**