composer: fixed dependency on really stable version of Symfony

Author: castamir

composer.json

@@ -15,9 +15,9 @@
         "joseki/utils": "^1.0",
         "nette/di": "~2.2",
         "nette/utils": "~2.2",
-        "symfony/console": "~2.7",
-        "symfony/config": "~2.7",
-        "symfony/yaml": "~2.7"
+        "symfony/console": "2.7.*",
+        "symfony/config": "2.7.*",
+        "symfony/yaml": "2.7.*"
     },
     "require-dev": {
         "nette/tester": "~1.0",