Give example of using modalEvent.relatedTarget to pass data from trigger element

Created by: cvrebert

I've seen a number of questions like this one: http://stackoverflow.com/q/24951453/3342739 Seems that some folks aren't making the connection that you can pass data from a trigger element to a modal initializer event callback by making use of event.relatedTarget and attributes (often data-*) on the trigger element, and thus adjust the modal's contents depending on which trigger button was clicked.