Support laravel 8 (#10)

Author: ziming

composer.json

@@ -14,14 +14,14 @@
     ],
     "require": {
         "php": ">=7.1",
-        "guzzlehttp/guzzle": "~6.0",
-        "illuminate/notifications": "~5.5 || ~6.0 || ~7.0",
-        "illuminate/support": "~5.5 || ~6.0 || ~7.0"
+        "guzzlehttp/guzzle": "~6.0|^7.0",
+        "illuminate/notifications": "~5.5 || ~6.0 || ~7.0 || ^8.0",
+        "illuminate/support": "~5.5 || ~6.0 || ~7.0 || ^8.0"
     },
     "require-dev": {
-        "illuminate/queue": "~5.5 || ~6.0 || ~7.0",
+        "illuminate/queue": "~5.5 || ~6.0 || ~7.0 || ^8.0",
         "mockery/mockery": "^1.2",
-        "phpunit/phpunit": "^8.5"
+        "phpunit/phpunit": "^8.5|^9.0"
     },
     "autoload": {
         "psr-4": {