title: proc_open error when try to run artisan dump-autoload
body: <p>When I try to run php artisan dump-autoload, I got this error:</p>
  
  <pre><code> root@server:/var/mysite# php artisan dump-autoload
   Generating optimized class loader
  
     [Symfony\Component\Process\Exception\RuntimeException]
     The Process class relies on proc_open, which is not available on your PHP installation.
  
   dump-autoload
  
   root@server:/var/mysite#
  </code></pre>
  
  <p>I'm on Ubuntu 12.10 x64 on DigitalOcean.</p>
  
  <p>any idea?</p>