[1.1] Update symfony versions in fat composer.json

bin/skeleton/fat_composer.json

 {
     "require": {
         "silex/silex": "~1.0",
-        "symfony/browser-kit": "~2.1",
-        "symfony/console": "~2.1",
-        "symfony/config": "~2.1",
-        "symfony/css-selector": "~2.1",
-        "symfony/dom-crawler": "~2.1",
-        "symfony/filesystem": "~2.1",
-        "symfony/finder": "~2.1",
-        "symfony/form": "~2.1",
-        "symfony/locale": "~2.1",
-        "symfony/process": "~2.1",
-        "symfony/security": "~2.1",
-        "symfony/serializer": "~2.1",
-        "symfony/translation": "~2.1",
-        "symfony/validator": "~2.1",
-        "symfony/monolog-bridge": "~2.1",
-        "symfony/twig-bridge": "~2.1",
+        "symfony/browser-kit": "~2.3",
+        "symfony/console": "~2.3",
+        "symfony/config": "~2.3",
+        "symfony/css-selector": "~2.3",
+        "symfony/dom-crawler": "~2.3",
+        "symfony/filesystem": "~2.3",
+        "symfony/finder": "~2.3",
+        "symfony/form": "~2.3",
+        "symfony/locale": "~2.3",
+        "symfony/process": "~2.3",
+        "symfony/security": "~2.3",
+        "symfony/serializer": "~2.3",
+        "symfony/translation": "~2.3",
+        "symfony/validator": "~2.3",
+        "symfony/monolog-bridge": "~2.3",
+        "symfony/twig-bridge": "~2.3",
         "doctrine/dbal": ">=2.2.0,<2.4.0-dev",
         "swiftmailer/swiftmailer": "5.*"
     }