Use a more strict PHP requirement (symfony-cmf/symfony-cmf#224)

Author: wouterj

composer.json

@@ -14,7 +14,7 @@
     "minimum-stability": "dev",
     "prefer-stable": true,
     "require": {
-        "php": ">=5.3.9",
+        "php": "^5.3.9|^7.0",
         "symfony/framework-bundle": "^2.3",
         "symfony-cmf/core-bundle": "^1.1.0-RC3",
         "doctrine/phpcr-bundle": "^1.1",