fix copy errors

plugins/symfony2/README.md

 # Symfony2
 
-This plugin provides completion for [symfony2](https://symfony.com/), as well as aliases for frequent composer commands.
+This plugin provides completion for [Symfony 2](https://symfony.com/), as well as aliases for frequent Symfony commands.
 
-To use it add composer to the plugins array in your zshrc file.
+To use it add symfony2 to the plugins array in your zshrc file.
 
 ```bash
 plugins=(... symfony2)