Merge pull request KnpLabs#434 from GrahamCampbell/patch-1

Bumped min versions to address the plugin interface issues

Author: cursedcoder

composer.json

@@ -20,14 +20,14 @@
         "php": "^5.5 || ^7.0",
         "psr/http-message": "^1.0",
         "psr/cache": "^1.0",
-        "php-http/httplug": "^1.0",
+        "php-http/httplug": "^1.1",
         "php-http/discovery": "^1.0",
         "php-http/client-implementation": "^1.0",
-        "php-http/client-common": "^1.1",
+        "php-http/client-common": "^1.3",
         "php-http/cache-plugin": "^1.2"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.0",
+        "phpunit/phpunit": "^4.0",
         "php-http/guzzle6-adapter": "^1.0",
         "guzzlehttp/psr7": "^1.2",
         "sllh/php-cs-fixer-styleci-bridge": "^1.3"