Added distance to prevent unintended reordering

Equivalent to Merge pull request #517 from ckosmowski/master on Jan 18,
2013 in the mleibman master.
Replace 'hover' deprecated pseudo-event

'hover' pseudo-event has been deprecated in jQuery 1.9.0,
use of 'mouseenter' and 'mouseleave' instead.

Copied from Jan 18, 2013 commit on mleibman master
Fix #520 - dropstart event not firing

Copied from mleibman Jan 18, 2013 commit