Omitted props fix is an API breakage

Hey all! Thanks for the awesome library.

I almost had a production issue on this, but fortunately caught it in testing. It seems that the props required by `SortableElement` HOC that previously passed through to the wrapper component are now intercepted and omitted. It also seems this was always the design, but it wasn't working until here: https://github.com/clauderic/react-sortable-hoc/compare/v1.10.0..v1.10.1#diff-2b4ca49d4bb0a774c4d4c1672d7aa781R23.

It just so happens that I was relying on `index` in a wrapped component and the side effect of no longer having `index` passed through was a showstopping breakage in my use case. This is not a complaint, I am just pointing out that this resulted in a breaking API change which was unexpected on a minor version bump, and I thought you'd appreciate a heads up.

Review the SortableElement HOC behavior and the v1.10.0..v1.10.1 comparison linked in the report, focusing on props that previously reached the wrapper component. The issue does not specify an intended fix; work is only complete after the project decides whether to restore compatibility or document and accept the API change.

Written by the indexing model from the issue text.