onSelection does not update

[Alex Kovar]

onSelection is being fed into the manager object on init:

https://github.com/davidtheclark/react-aria-menubutton/blob/master/src/Wrapper.js#L26

If this prop later changes, it does not update in the component.

[Ainur]

For a while, I decided to force-update a whole select component via key prop, which takes a variable that makes the onSelect different

[Monroe Ekilah]

This just bit me and it was a tricky bug to narrow down! Props should never be saved like this in React in a constructor without being updated in lifecycle methods like componentDidUpdate or getDerivedStateFromProps

[Monroe Ekilah]

Added a fix for this in #151