Allow to use the internal PHP server

Little hack found on Silex documentation:
    http://silex.sensiolabs.org/doc/web_servers.html#php-5-4

To run the server:
    php -S 127.0.0.1:8080 index.php
Merge pull request #45 from GromNaN/internal-server

Allow to use the internal PHP server, thanx @GromNaN