Update Composer for Laravel 5.8 compatibility

Author: Lloople

composer.json

@@ -12,16 +12,16 @@
     ],
     "require": {
         "php": "^7.0",
-        "illuminate/contracts": "5.5.*|5.6.*|5.7.*",
-        "illuminate/support": "5.5.*|5.6.*|5.7.*",
+        "illuminate/contracts": "5.5.*|5.6.*|5.7.*|5.8.*",
+        "illuminate/support": "5.5.*|5.6.*|5.7.*|5.8.*",
         "graham-campbell/manager": "^3.0|^4.0",
         "pusher/pusher-php-server": "^3.3"
     },
     "require-dev": {
         "graham-campbell/analyzer": "^1.1",
         "graham-campbell/testbench": "^4.0|^5.0",
         "mockery/mockery": "^1.0",
-        "orchestra/testbench": "3.5.*|3.6.*|3.7.*",
+        "orchestra/testbench": "3.5.*|3.6.*|3.7.*|3.8.*",
         "phpunit/phpunit": "^6.5|^7.0"
     },
     "autoload": {