add update hint

README.md

@@ -12,3 +12,13 @@ What's inside
   * [linum-plus](https://github.com/emacsmirror/linum-plus)
   * [markdown-mode](https://github.com/emacsmirror/markdown-mode)
   * [yaml-mode](https://github.com/yoshiki/yaml-mode)
+
+
+Update
+------
+
+```sh
+cd ~/.emacs.d
+git pull
+git submodule update --init --recursive
+```