added missing installation section in the HttpFoundation docs

Author: fabpot

components/http_foundation.rst

@@ -15,6 +15,15 @@ generated by some functions (``echo``, ``header``, ``setcookie``, ...).
 The Symfony2 HttpFoundation component replaces these default PHP global
 variables and functions by an Object-Oriented layer.
 
+Installation
+------------
+
+You can install the component in many different ways:
+
+* Use the official Git repository (https://github.com/symfony/HttpFoundation);
+* Install it via PEAR ( `pear.symfony.com/HttpFoundation`);
+* Install it via Composer (`symfony/http-foundation` on Packagist).
+
 Request
 -------