title: Sliex ~2.0 difference between download and composer - e.g missing ServiceProviderInterface
body: <p>If I download the <a href="http://silex.sensiolabs.org/get/silex_fat.tgz" rel="nofollow">fat archive</a> linked here <a href="http://silex.sensiolabs.org/download" rel="nofollow">http://silex.sensiolabs.org/download</a> I get a different silex to that when I composer require "~2.0" ( as instructed on the same page ) , for example, the ServiceProviderInterace does not exist in silex/src/Silex in the composer version, whereas in the fat archive it does. Looking at github the composer version matches...but I need the version with the ServiceProviderInterface...</p>
  
  <p>I must be doing something wrong! advice please</p>