Make sure to use a plugin version with correct interface

Author: sagikazarmark

composer.json

@@ -20,7 +20,7 @@
         "php-http/client-implementation": "^1.0",
         "php-http/message-factory": "^1.0.2",
         "php-http/client-common": "^1.1",
-        "php-http/plugins": "^1.0",
+        "php-http/plugins": "^1.1",
         "symfony/options-resolver": "^2.7|^3.0",
         "symfony/framework-bundle": "^2.7|^3.0"
     },