fix: updated to monolog 2.0

Author: jhull

composer.json

@@ -5,7 +5,7 @@
   "require": {
     "php": ">=5.5",
     "guzzlehttp/guzzle": "^6.3",
-    "monolog/monolog": ">=1.0"
+    "monolog/monolog": "^2.0"
   },
   "require-dev": {
     "phpunit/phpunit": "^6.0"