Using latest version of discovery

Author: Nyholm

composer.json

@@ -13,7 +13,7 @@
         "symfony/options-resolver": "^2.6|^3.0",
         "php-http/httplug": "^1.0",
         "php-http/message-factory": "^1.0.2",
-        "php-http/discovery": "^0.8"
+        "php-http/discovery": "^0.9"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8",