Fix for package

 - Specify minimum Emacs version
 (defvar-local, setq-local were introduced at Emacs 24.3)
 - Fix group name
 - Add autoload cookie for lazy loading

And I think it is better to use `defface` instead of `make-face` + `set-face-attribute`.

Reference
  http://www.gnu.org/software/emacs/manual/html_node/elisp/Defining-Faces.html