breaking(DropdownItem): callback with (e, props) onClick

[levithomason]

Breaking Change

Fixes #804.

This PR updates DropdownItem onClick to callback with the event and all props. Previously it called back with the event and value, but the docs stated it also called back with the text.

Upgrade Guide

The second DropdownItem onClick parameter is now the full props object.

BEFORE

const handleItemClick = (e, value) => {
  console.log('You clicked:', value)
}

<DropdownItem onClick={handleClick} />

AFTER

const handleItemClick = (e, props) => {
  console.log('You clicked:', props.value)
}

<DropdownItem onClick={handleClick} />