Fix position of choices container when input element moves to another location

[tiagoschenkel]

This merge request solves the problem reported in issue #2259.

The problem happens because the Popper component used to render the choices is a stateless component. Since the Popper component receives a reference to the inputEl component, the render method is unable to detect when the original inputEl moved to another place.

I noticed that when the original input element moves, React is keeping the old Popper component without forcing it to redraw.

My solution is based on this example from Material-UI docs:
https://v1-5-0.material-ui.com/utils/popper/#faked-reference-object

I'm keeping an object that has a reference to the last position of the inputEl and updating this object only when the inputEl moves. Doing this we only force the redraw of the Popper container only when needed.

Fixes #2259.

[djhi]

Awesome! Thanks!