Merge pull request #157 from sendinblue/update-guzzle

Restrict guzzle to v7.0 due to breaking changes in v7.2

Author: rajatsib

composer.json

@@ -22,7 +22,7 @@
         "ext-curl": "*",
         "ext-json": "*",
         "ext-mbstring": "*",
-        "guzzlehttp/guzzle": "^6.2 || ^7.0"
+        "guzzlehttp/guzzle": "^6.2 || ~7.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8",