add guzzle7 to require (#26)

Author: swilla

composer.json

@@ -17,7 +17,7 @@
     ],
     "require": {
         "php": "^7.1",
-        "guzzlehttp/guzzle": "~6.0",
+        "guzzlehttp/guzzle": "~6.0 || ~7.0",
         "illuminate/support": "5.7.* || 5.8.* ||^6.0 || ^7.0 || ^8.0",
         "symfony/dotenv": "^4.2 || ^5.1"
     },