Update Composer to use version 2.0 of php-http/httplug and php-http/client-integration-tests

Author: timoschinkel

composer.json

@@ -16,13 +16,13 @@
     ],
     "require": {
         "php": "^7.0",
-        "php-http/httplug": "^1.0",
+        "php-http/httplug": "^2.0",
         "guzzlehttp/guzzle": "^5.1",
         "php-http/discovery": "^1.0"
     },
     "require-dev": {
         "ext-curl": "*",
-        "php-http/client-integration-tests": "^0.5.1",
+        "php-http/client-integration-tests": "^2.0",
         "guzzlehttp/ringphp": "^1.1"
     },
     "provide": {