update composer.json for Symfony 2.4

Author: reecefowell

composer.json

@@ -15,9 +15,9 @@
     "minimum-stability": "dev",
     "require": {
         "php": ">=5.3.3",
-        "symfony/symfony": "2.3.*",
-        "doctrine/orm": ">=2.2.3,<2.4-dev",
-        "doctrine/doctrine-bundle": "1.2.*",
+        "symfony/symfony": "2.4.*",
+        "doctrine/orm": "~2.2,>=2.2.3",
+        "doctrine/doctrine-bundle": "~1.2",
         "knplabs/knp-paginator-bundle": "2.3.*"
     },
     "require-dev": {