Added support for laravel 6.0 .

.travis.yml

@@ -54,6 +54,12 @@ matrix:
   - php: 7.3
     env: LARAVEL=5.8.* PHPUNIT=~8.0
     
+  # Laravel 6.0
+  - php: 7.2
+    env: LARAVEL=6.0.* PHPUNIT=~8.0
+  - php: 7.3
+    env: LARAVEL=6.0.* PHPUNIT=~8.0
+    
 before_install:  
   - travis_retry composer self-update
   - travis_retry composer require laravel/framework:$LARAVEL --no-update --no-interaction

composer.json

@@ -10,14 +10,14 @@
     ],
     "license": "Apache-2.0",
     "require": {
-    	"laravel/framework": "~5.1",
+    	"laravel/framework": "~5.1|~6.0",
     	"casbin/casbin": "~1.0"
     },
     "require-dev": {
         "phpunit/phpunit": "~5.7|~6.0|~7.0|~8.0",
         "php-coveralls/php-coveralls": "^2.1",
         "mockery/mockery": "^1.0",
-        "laravel/laravel": "~5.1"
+        "laravel/laravel": "~5.1|~6.0"
     },
     "autoload": {
         "psr-4": {