Implement Positioned Overlay Component

[mfunkie]

Ideally the API would look somewhat similar to React Bootstrap's OverlayTrigger, but instead of being triggered, the Overlay would always display if it is in the render tree.

I'm looking to add the following parameters

placement: top, right, bottom, left
anchor: top, right, bottom, left. Anchor would respect top and bottom for right or left placed elements, and left and right for top or bottom placed elements. Anchor would set the top left of the Overlayed element based on the positioning of the element passed as children.

A planned implementation would look like

<PositionedOverlay overlay={<div>I am an overlay</div>} placement='bottom' anchor='right'>
  <button>I am the button to anchor around</button>
</PositionedOverlay>