Update quick.md

Since there is a SO-thread with around 5000 views and counting,  this is certainly something that should appear in the quickstart.

http://stackoverflow.com/questions/17990820/set-port-for-php-artisan-php-serve/19944781

quick.md

@@ -43,6 +43,10 @@ After installing Laravel, you may need to grant the web server write permissions
 Typically, you may use a web server such as Apache or Nginx to serve your Laravel applications. If you are on PHP 5.4+ and would like to use PHP's built-in development server, you may use the `serve` Artisan command:
 
 	php artisan serve
+
+By default the HTTP-server will listen to port 8000. However if that port is already in use or you wish to serve multiple applications this way, you might want to specify what port to use. Just add the --port argument:
+
+	php artisan serve --port=8080
 
 <a name="directories"></a>
 ### Directory Structure