Register event subscriber in the boot method

The Pimple::extend method was registering the listener each time it id called.

AcceptHeaderServiceProvider.php

@@ -11,19 +11,16 @@ public function register(Application $app)
     {
         $app['route_class'] = '\\Pff\\ServiceProvider\\AcceptHeaderServiceProvider\\Route';
 
-        $app['dispatcher'] = $app->extend('dispatcher', function($dispatcher) {
-            $dispatcher->addSubscriber(new KernelListener());
-            return $dispatcher;
-        });
-
         $app['url_matcher'] = $app->share(function () use ($app) {
             $matcher =  new UrlMatcher($app['routes'], $app['request_context']);
             $matcher->setRequest($app['request']);
+
             return $matcher;
         });
     }
 
     public function boot(Application $app)
     {
+        $app['dispatcher']->addSubscriber(new KernelListener());
     }
 }