`register_nav_menus()` automatically takes care of `add_theme_support('menus')`

`register_nav_menus()` automatically takes care of
`add_theme_support('menus')`
so this is not needed.

"This function automatically registers custom menu support for the
theme therefore you do not need to call add_theme_support( 'menus' ); "
Soruce: http://codex.wordpress.org/Function_Reference/register_nav_menus