Fixed using angular2-draggable with a scaled parent elment

[synnottd]

This fixes the problem outlined here: #31.

Note: I fixed for a parent with scaling not the element itself.

I work with the OP and it became necessary for us to get this working.

The issues occurs if there is a CSS transform scale on a parent of the element you want to drag. The errors are that the element is transformed by the unscaled distance, meaning the element effectively is transformed visibly by the distance * scale, meaning the cursor and the element become de-synced. It will also move out of bounds if bounds are set.

I fixed these problems by dividing anything changing AngularDraggableDirective.tempTrans by the scale. I decided the best way to know the scale is to require the user to pass it in as an Input. You could probably use window.getComputedStyle() to work it out, but it seems overkill to do this.

[xieziyu]

Great! Thanks for your contribution. I agree with your design.

[xieziyu]

I tested your changes. It seems the calculation will bring other issues.
So I have to revert that part of your changes.

[synnottd]

Would you mind elaborating? I'm more than happy to fix it.