Added tests for "menus.models.Menu".
Added tests for "menus.models.Link" and refactored its get_absolute_url method.
Added tests for "menus.models.Bookmark" and improved Link's unicode representation.
Added tests for "menus.utils.(create/delete)_bookmarks".
Added tests for "menus.utils.create_detail_navigation".
Added tests for "menus.utils.create_(detail/list)_actions".