Allow discovery version 0.5

Author: Nyholm

composer.json

@@ -16,7 +16,7 @@
         "symfony/symfony":"~2.7|~3.0",
         "sensio/framework-extra-bundle": "~2.7|~3.0",
         "php-http/httplug": "1.0.0-beta",
-        "php-http/discovery": "^0.4",
+        "php-http/discovery": "^0.4|^0.5",
         "php-http/plugins": "dev-master",
         "php-http/client-implementation": "1.0",
         "psr/log": "1.0.0"