Use PSR-4 everywhere instead of PSR-0

Author: Tobion

composer.json

@@ -22,9 +22,8 @@
         "symfony/phpunit-bridge": "~2.7"
     },
     "autoload": {
-        "psr-0": { "Symfony\\Component\\OptionsResolver\\": "" }
+        "psr-4": { "Symfony\\Component\\OptionsResolver\\": "" }
     },
-    "target-dir": "Symfony/Component/OptionsResolver",
     "minimum-stability": "dev",
     "extra": {
         "branch-alias": {