Added Laravel 5.6 support

Author: Willem Oostendorp

composer.json

@@ -8,8 +8,8 @@
         "symfony/workflow": "^3.3",
         "symfony/process": "^3.3",
         "symfony/event-dispatcher": "^3.3",
-        "illuminate/console": "5.3.* | 5.4.* | 5.5.*",
-        "illuminate/support": "5.3.* | 5.4.* | 5.5.*"
+        "illuminate/console": "5.3.* | 5.4.* | 5.5.* | 5.6.*",
+        "illuminate/support": "5.3.* | 5.4.* | 5.5.* | 5.6.*"
     },
     "autoload": {
         "psr-4": {
@@ -36,6 +36,6 @@
     },
     "require-dev": {
         "mockery/mockery": "^0.9.8",
-        "phpunit/phpunit": "^6.0"
+        "phpunit/phpunit": "^6.0|~7.0"
     }
 }