chown and chgrp should also accept int as owner and group

Filesystem.php

@@ -211,7 +211,7 @@ public function chmod($files, $mode, $umask = 0000, $recursive = false)
      * Change the owner of an array of files or directories.
      *
      * @param string|iterable $files     A filename, an array of files, or a \Traversable instance to change owner
-     * @param string          $user      The new owner user name
+     * @param string|int      $user      A user name or number
      * @param bool            $recursive Whether change the owner recursively or not
      *
      * @throws IOException When the change fails
@@ -238,7 +238,7 @@ public function chown($files, $user, $recursive = false)
      * Change the group of an array of files or directories.
      *
      * @param string|iterable $files     A filename, an array of files, or a \Traversable instance to change group
-     * @param string          $group     The group name
+     * @param string|int      $group     A group name or number
      * @param bool            $recursive Whether change the group recursively or not
      *
      * @throws IOException When the change fails