SlideChangeEvent position is not set

[javier-godoy]

As mentioned in #10 (comment), the position member variable of SlideChangeEvent is not set from its constructor:

CarouselAddon/src/main/java/com/flowingcode/vaadin/addons/carousel/Carousel.java

Lines 187 to 190 in e4744e2

	public SlideChangeEvent(
	Carousel source, boolean fromClient, @EventData("event.detail.value") String position) {
	super(source, true);
	}