API：http://www.tutorialspoint.com/html5/html5_drag_drop.htm

example：http://jsfiddle.net/bNQeJ/4/

注意点：http://stackoverflow.com/questions/8801816/drag-drop-html-5-jquery-how-to-fire-the-drop-event

备注：According to this you need to call event.preventDefault on the last dragenter or dragover event to create a valid drop target.

html5 drag and drop with jquery