Update versions in README.md (#101)

Author: lildude

README.md

@@ -19,9 +19,9 @@ The development of phpSmug takes place in my free time. If you find phpSmug usef
 
 ## Requirements
 
-* PHP >= 7.3.0,
-* [Guzzle 6](https://github.com/guzzle/guzzle) library and the [Guzzle OAuth1 Subscriber](https://github.com/guzzle/oauth-subscriber),
-* (optional) [PHPUnit](https://phpunit.de/) and [php-cs-fixer](http://cs.sensiolabs.org/) to run tests.
+* PHP >= 8.1.0,
+* [Guzzle 7](https://github.com/guzzle/guzzle) library and the [Guzzle OAuth1 Subscriber](https://github.com/guzzle/oauth-subscriber),
+* (optional) [PHPUnit](https://phpunit.de/) to run tests.
 
 ## Installation