Moved composed sort callbacks into closure

This should fix a problem I had, in which multiple sortables in a document clobbered up each others scope.
For example, updating a REST resource in the stop callback didn't work, because always the route of the last sortable in the DOM was called.
forgot a curley
Merge pull request #451 from skahlert/patch-sortable-clobber

Poposed fix for issue #450