When the body is scrolled, dragging acts as if it's not scrolled.

I can reproduce this using the demo:
https://clauderic.github.io/react-sortable-hoc/#/basic-configuration/basic-usage?_k=00cf93

Add these styles to `.Showcase__style__list Showcase__style__stylizedList`:
``` css
height: 100vh;
overflow: visible;
```


Scroll down (which scrolls down the body) and try clicking and dragging an item. It moves the item relative to `scrollTop` of `0`, not `scrollTop` of wherever your `body` is at.