fix(IE): Replace .bind(this) with angular.bind(this, fn) to make it work for IE7/8
fix(*): destroy draggable/droppable if an element having the directive is removed to avoid DOM leaks
fix(*): Closes #67 - data prefix support for jqyoui-draggable/jqyoui-droppable
fix(*): Closes #71 - zIndex issue with helper:clone
chore(*): version bump 1.0.6

  - Support for IE7/8
  - Fix DOM leak
  - Support data- prefix for jqyoui-draggable and jqyoui-droppable
  - Fix zIndex issue with helper:clone option