adjust testing component dependency

Author: lsmith77

composer.json

@@ -24,7 +24,7 @@
     },
     "require-dev": {
         "symfony-cmf/routing-bundle": "~1.2,>=1.2.0",
-        "symfony-cmf/testing": "dev-lowest_versions",
+        "symfony-cmf/testing": "~1.2,>=1.2.6",
         "sonata-project/doctrine-phpcr-admin-bundle": "~1.1",
         "symfony/monolog-bundle": "~2.3"
     },