Update composer.json for Laravel 6.0

Author: divdax

composer.json

@@ -39,13 +39,13 @@
         }
     ],
     "require": {
-        "php": ">=7.1.3",
-        "illuminate/console": "^5.8",
-        "illuminate/database": "^5.8",
-        "illuminate/filesystem": "^5.8"
+        "php": ">=7.2",
+        "illuminate/console": "^6.0",
+        "illuminate/database": "^6.0",
+        "illuminate/filesystem": "^6.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.5",
+        "phpunit/phpunit": "^8.0",
         "mockery/mockery": "^1.0",
         "orchestra/testbench": "^3.8"
     },