Horizontal Drop-Down Menu
To add a top-level menu item with no dropdown, the solution was to link the js file to the non-minimised version then:
This could be done easily:
In the JS, change $menuItems = $listItems.children( 'a' ), to $menuItems = $listItems.children( 'a.dropdown' ),
then, In the HTML, add a class="dropdown" to the href (not the list item) wherever you have subitems and need a dropdown.