Merge pull request #173 from EgorGruzdev/master

Fix doctype declaration for rule method. Allows both array and string for $field parameter

src/Valitron/Validator.php

@@ -1084,7 +1084,7 @@ class Validator
      * Convenience method to add a single validation rule
      *
      * @param  string|callback           $rule
-     * @param  array                     $fields
+     * @param  array|string              $fields
      * @return $this
      * @throws \InvalidArgumentException
      */