Rename Symfony2 / Symfony3 to just Symfony (#756)

README.md

 * [Nette](https://nette.org) - Another framework comprised of individual components.
 * [Phalcon](https://phalconphp.com/en/) - A framework implemented as a C extension.
 * [PPI Framework 2](http://www.ppi.io) - An interoperability framework.
-* [Symfony 3](http://symfony.com/) - A framework comprised of individual components (SF3).
+* [Symfony](https://symfony.com/) - A framework comprised of individual components (SF).
 * [Yii2](https://github.com/yiisoft/yii2/) - Another PHP framework.
 * [Zend Framework 2](https://framework.zend.com) - Another framework comprised of individual components (ZF2).
 * [Radar](https://github.com/radarphp/Radar.Adr) - An Action-Domain-Responder implementation for PHP.
 *Extras related to web development frameworks.*
 
 * [CakePHP CRUD](https://github.com/friendsofcake/crud) - A Rapid Application Development (RAD) plugin for CakePHP.
-* [Knp RAD Bundle](http://rad.knplabs.com/) - A Rapid Application Development (RAD) bundle for Symfony 2.
+* [Knp RAD Bundle](http://rad.knplabs.com/) - A Rapid Application Development (RAD) bundle for Symfony.
 * [Symfony CMF](https://github.com/symfony-cmf/symfony-cmf) - A Content Management Framework to create custom CMS.
 
 ## Components
 * [CakePHP Plugins](http://plugins.cakephp.org/) - A directory of CakePHP plugins.
 * [Hoa Project](https://hoa-project.net/En/) - Another package of PHP components.
 * [League of Extraordinary Packages](https://thephpleague.com/) - A PHP package development group.
-* [Symfony2 Components](http://symfony.com/doc/master/components/index.html) - The components that make Symfony 2.
+* [Symfony Components](http://symfony.com/doc/master/components/index.html) - The components that make Symfony.
 * [Zend Framework 2 Components](https://packages.zendframework.com/) - The components that make Zend Framework.
 
 ## Micro Frameworks
 * [Bullet PHP](http://bulletphp.com/) - A micro framework for building REST APIs.
 * [Lumen](https://lumen.laravel.com) - A micro-framework by Laravel.
 * [Proton](https://github.com/alexbilbie/Proton) - A StackPHP compatible micro framework.
-* [Silex](http://silex.sensiolabs.org/) - A micro framework built around Symfony2 components.
+* [Silex](http://silex.sensiolabs.org/) - A micro framework built around Symfony components.
 * [Slim](https://www.slimframework.com/) - Another simple micro framework.
 
 ## Micro Framework Extras
 * [Container](https://github.com/thephpleague/container) - Another flexible dependency injection container.
 * [PHP-DI](http://php-di.org/) - A dependency injection container that supports autowiring.
 * [Pimple](http://pimple.sensiolabs.org/) - A tiny dependency injection container.
-* [Symfony DI](https://github.com/symfony/dependency-injection) - A dependency injection container component (SF2).
+* [Symfony DI](https://github.com/symfony/dependency-injection) - A dependency injection container component (SF).
 
 ## Imagery
 *Libraries for manipulating images.*
 * [Spork](https://github.com/kriswallsmith/spork) - A process forking library.
 * [Sslurp](https://github.com/EvanDotPro/Sslurp) - A library that makes dealing with SSL suck less.
 * [SuperClosure](https://github.com/jeremeamia/super_closure) - A library that allows Closures to be serialized.
-* [Symfony VarDumper](http://symfony.com/doc/current/components/var_dumper/introduction.html) - A variable dumper component (SF2).
+* [Symfony VarDumper](http://symfony.com/doc/current/components/var_dumper/introduction.html) - A variable dumper component (SF).
 * [Underscore](http://anahkiasen.github.io/underscore-php/) - A PHP port of the Underscore JS library.
 * [Whoops](https://github.com/filp/whoops) - A pretty error handling library.