Fixed Draggable on Safari and mobile Safari

webkitMovementX and webkitMovementY are not currently supported in the version of webkit that ships with Safari (OS X 10.9.2) and mobile Safari (iOS 7.1).

Reverted the position delta tracking (as seen in this commit) to the manual calculation instead of relying on the webkitMovement properties.
Removed a few errant minus signs that accidentally got pasted in
Added a missing emit
Fixed an indentation error
Merge pull request #52 from jimray/master

Fixed Draggable on Safari and mobile Safari