Using stable version of discovery

Author: Nyholm

composer.json

@@ -14,7 +14,7 @@
         "php": "^5.5|^7.0",
         "psr/http-message": "^1.0",
         "php-http/message-factory": "^1.0",
-        "php-http/discovery": "^0.9"
+        "php-http/discovery": "^1.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^5.4",