Upgrade justinrainbow/json-schema

Author: amenophis

composer.json

@@ -41,7 +41,7 @@
     "require": {
         "php": "~7.0",
         "guzzlehttp/guzzle": "~6.1",
-        "justinrainbow/json-schema": "~3.0.0"
+        "justinrainbow/json-schema": "~5.2"
     },
     "require-dev": {
         "phpunit/phpunit": "~4.0",