Reverting of $.UIkit.tab availability

It was removed here: https://github.com/uikit/uikit/commit/2f8a8b559463f3a8068b3326874827e0ef00e895#diff-ce215d94a52d449f1a34f292126608d7L60

I'm using it to connect connect switcher. But connect by natural position in dom, not by ID.
Example how I use it: https://github.com/nazar-pc/CleverStyle-CMS/blob/b1b9ed3cabd3d19cd66ece24d75575df0f30ca75/includes/js/jquery.cs-helper.coffee#L87

Patch is very simple, I hope you will accept it.