Fix autoload.files setting in composer.json

See zendframework/zf2#3715


> This currently breaks my application with
> 
> ```
Fatal error: require(): Failed opening required '/.../vendor/zendframework/zend-stdlib/compatibility/autoload.php' (include_path='.:/usr/local/Cellar/php54/5.4.11/lib/php') in /.../vendor/composer/autoload_real.php on line 43```