Use Github links for Symfony components.

README.md

 * [PHP VCR](https://php-vcr.github.io/) - A library for recording and replaying HTTP requests.
 * [Requests](https://github.com/rmccue/Requests) - A simple HTTP library.
 * [Retrofit](https://github.com/tebru/retrofit-php) - A library to ease creation of REST API clients.
-* [Symfony HTTP Client](https://symfony.com/doc/current/components/http_client.html) - A component to fetch HTTP resources synchronously or asynchronously.
+* [Symfony HTTP Client](https://github.com/symfony/http-client) - A component to fetch HTTP resources synchronously or asynchronously.
 * [zend-diactoros](https://github.com/zendframework/zend-diactoros) - PSR-7 HTTP Message implementation.
 
 ### Scraping
 * [Slimdump](https://github.com/webfactory/slimdump) - An easy dumper tool for MySQL.
 * [Spork](https://github.com/kriswallsmith/spork) - A process forking library.
 * [SuperClosure](https://github.com/jeremeamia/super_closure) - A library that allows Closures to be serialized.
-* [Symfony VarDumper](https://symfony.com/doc/current/components/var_dumper.html) - A variable dumper component (SF).
+* [Symfony VarDumper](https://github.com/symfony/var-dumper) - A variable dumper component (SF).
 * [Underscore](https://anahkiasen.github.io/underscore-php/) - A PHP port of the Underscore JS library.
 * [Whoops](https://github.com/filp/whoops) - A pretty error handling library.