Minimal required CSS

[ishirav]

This library is awesome!
One small comment: the documentation should include a note about the minimal CSS required for this to work. AFAIK the container should have position: relative and the items should have position: absolute. Otherwise nothing happens, and there's no clue why.

[ishirav]

Also, the option to add a .position-highlight element for showing where the drop will occur is not documented.