Allow guzzle 7

Author: mattwire

composer.json

@@ -42,7 +42,7 @@
         "ext-json": "*"
     },
     "replace": {
-      "guzzlehttp/guzzle": "^6",
+      "guzzlehttp/guzzle": "^6.5 || ^7.0",
       "guzzlehttp/psr7": "^1",
       "psr/http-message-implementation": "^1.0",
       "psr/log" : "^1",