🐛 update casbin version

fixed Class 'Casbin\Log\Log' not found should use casbin >= 0.2.1

Author: osindex

composer.json

@@ -11,7 +11,7 @@
     "license": "Apache-2.0",
     "require": {
     	"laravel/framework": "~5.1",
-    	"casbin/casbin": ">=0.1.0"
+    	"casbin/casbin": ">=0.2.1"
     },
     "require-dev": {
         "phpunit/phpunit": "~5.7|~6.0|~7.0|~8.0",