Merge pull request #15 from veewee/php80

Allow PHP 8.0

Author: dbu

composer.json

@@ -11,7 +11,7 @@
         }
     ],
     "require": {
-        "php": "^7.1 || ^7.0",
+        "php": "^7.0 || ^8.0",
         "psr/log": "^1.0",
         "php-http/client-common": "^1.9 || ^2.0",
         "php-http/message": "^1.0",