Fix bug on rotation ?

An attempt to fixe the issue #42 https://github.com/amasciul/Drinks/issues/42

I call manually the onScrollChanged during the onPreDraw so that the scrollView.getScrollY() return the correct value and not 0, but for some reasons that I don't know the bottom and top are modify after that.

So I try to find a work around and not use setBottom and setTop that are "meant to be called by the layout" according to the doccumentation.

```
Sets the bottom position of this view relative to its parent. This method is meant to be called by the layout system and should not generally be called otherwise, because the property may be changed at any time by the layout.
```

At the end, my solution relies on paddings and margins, that might not be very elegant but it seems to work as intended.