minor #1004 Register clean up (henrikbjorn)

This PR was squashed before being merged into the 2.0.x-dev branch (closes #1004).

Discussion
----------

Register clean up

Commits
-------

354b7663 Register clean up

src/Silex/Application.php

@@ -143,11 +143,7 @@ class Application extends Container implements HttpKernelInterface, TerminableIn
     {
         $this->providers[] = $provider;
 
-        $provider->register($this);
-
-        foreach ($values as $key => $value) {
-            $this[$key] = $value;
-        }
+        parent::register($provider, $values);
 
         return $this;
     }
@@ -160,7 +156,10 @@ class Application extends Container implements HttpKernelInterface, TerminableIn
      */
     public function boot()
     {
-        if (!$this->booted) {
+        if ($this->booted) {
+            return;
+        }
+
         $this->booted = true;
 
         foreach ($this->providers as $provider) {
@@ -173,7 +172,6 @@ class Application extends Container implements HttpKernelInterface, TerminableIn
             }
         }
     }
-    }
 
     /**
      * Maps a pattern to a callable.