Sortable CSS class remain if drag and drop fails

[kkotosky]

To recreate:
Open a select multiple with sortable = true;
Select many items.
Drag one items across all of the other items quickly.
Drop your item in a location such that the tag is put in its original location.
dropping, dropping-before and dropping-after classes will remain on other tags even though dropping in no longer happening

[idozorenko]

I couldn't find a reasonable solution for this bug. Also there are some major bugs with sorting, like item is not moved on drop or moved into a wrong place (IMHO implementation is very poor), so I've rewritten uiSelectSort directive completely. I can create PR if anyone is interested.

[user378230]

This should have been resolved by #902, though it is not yet released.

[user378230]

Closing #902 released.