Feature/upgrade guzzle version (#57)

Author: Alex-DA

composer.json

@@ -5,7 +5,7 @@
   "require": {
     "php": ">=5.4.0",
     "aws/aws-sdk-php": "^3.52",
-    "guzzlehttp/guzzle": "^6.3",
+    "guzzlehttp/guzzle": "^6.2.1|^7.0",
     "mtdowling/jmespath.php": "^2.4",
     "psr/http-message": "^1.0"
   },