dragging within a relative parent causes text to display incorrectly

[Progdom]

When trying to use this in a modal that is relative the sortable elements display incorrectly. This is due to that fact that it initially bases the top of the element from the document body, but then displays the moveUpdate from the nearest parent. This causes it to be displayed completely off of the cursor. I have a forked version which fixes this issue. It requires an additional attribute that tells the directive the element class/id to use as the actual parent, this way the offset is correct.

[ghost]

Any chance of getting a PR in? I could use this functionality in something I'm working on.