Remove rotation functionality from DistortableImageOverlay.
Begin enabling user interactions and integrating editing handles.
Normalize transform-origin rule for all browsers using L.DomUtil.TRANSFORM.
Add #getCenter back to DistortableImageOverlay.
Add rotation and scaling interactions to RotateHandle. Implement RotateHandle#_calculateAngle using the law of cosines.
Switch angular displacement calculation to Jeff's method using Math.atan2 (rather than the law of cosines).
Implement WarpHandle.
Edit DistortableImage.Edit#changeMode and add #_rotateBy and #_scaleBy. Implement dragging behavior by overriding the _updatePosition method of the L.Draggable instance, rather than by listening on 'dragstart', 'drag', and 'dragend' events.
Add _leaflet_pos property (fix bug w/ L.Draggable). Add #getCorners method.
Remove extraneous methods from EditHandle.js
Add comment explaining the purpose of L.MatrixUtil.multsm.
Write tests for L.DistortableImage.Edit and L.RotateHandle. Add sinon.js as a dependency.