Use Symfony ~2.8 or ~3.0

Author: bytehead

composer.json

@@ -4,7 +4,7 @@
     "type": "symfony-bundle",
     "require": {
         "contao/core-bundle": "^4.2",
-        "symfony/console": "^2.8",
+        "symfony/console": "~2.8|~3.0",
         "contao/installation-bundle": "^1.1"
     },
     "autoload": {