Don't initialize Sortable just for destroying

The `:ui-sortable` pseudo-selector filters out the element if it hasn't been initialized as a Sortable.
Merge pull request #494 from atesgoral/master

Improve jQuery UI Sortable fix
Fix #498 - Selections are not always maintained when filtering (Example 4).
Fix #496 - Improve the example to demonstrate proper use.
Merge remote-tracking branch 'mleibman/master'