Use native class instead of EmberObject.extend

[jelhan]

Refactor history service to a native class.

ember-cli-browser-navigation-button-test-helpers/addon-test-support/index.js

Lines 27 to 51 in e97905f

	const history = Service.create({
	addHistory() {
	const currentURL = this.router.get('currentURL');
	this.history.push(currentURL);
	},
	history: [],
	forward: [],
	goBack() {
	// last element in router.history is current page
	// remove it from history and apply to forward list
	const currentURL = this.history.pop();
	this.forward.push(currentURL);
	// get the page before is our target
	// remove that one also, since it's readded by transition
	const previousURL = this.history.pop();
	assert('There were no URLs in the browser history. Make sure a transition ocurred after `setupBrowserNavigationButtons` was called.', previousURL);
	return this.router.transitionTo(previousURL);
	},
	goForward() {
	const nextURL = this.forward.pop();
	assert('backButton must be used at least once before forwardButton can be used.', nextURL);
	return this.router.transitionTo(nextURL);
	},
	router
	});