Update composer dependency versions for Laravel 8 (#40)

Author: corsair

composer.json

@@ -20,7 +20,7 @@
     "require": {
         "php": "^7.2",
         "ext-json": "*",
-        "guzzlehttp/guzzle": "^6.3",
+        "guzzlehttp/guzzle": "^6.3 || ^7.0.1",
         "illuminate/notifications": "^6.0 || ^7.0 || ^8.0",
         "illuminate/support": "^6.0 || ^7.0 || ^8.0",
         "illuminate/queue": "^6.0 || ^7.0 || ^8.0",
@@ -30,7 +30,7 @@
     "require-dev": {
         "mockery/mockery": "^1.3",
         "orchestra/testbench": "^5.0 || ^6.0",
-        "phpunit/phpunit": "^8.5"
+        "phpunit/phpunit": "^8.5 || ^9.0"
     },
     "autoload": {
         "psr-4": {