PhpSpec compatibility

Author: xabbuh

composer.json

@@ -26,7 +26,7 @@
         "psr/http-message": "^1.0"
     },
     "require-dev": {
-        "phpspec/phpspec": "^2.4",
+        "phpspec/phpspec": "^5.0 || ^6.0 || ^7.0",
         "php-http/mock-client": "^1.2",
         "php-xapi/test-fixtures": "^1.0",
         "symfony/phpunit-bridge": "^5.2"