Merge pull request #280 from snapshotpl/http-status-103-early-hints

Add early hint status code

Author: weierophinney

src/Response.php

@@ -35,6 +35,7 @@ class Response implements ResponseInterface
         100 => 'Continue',
         101 => 'Switching Protocols',
         102 => 'Processing',
+        103 => 'Early Hints',
         // SUCCESS CODES
         200 => 'OK',
         201 => 'Created',