Updated android support

This release fixes a number of bugs and includes a breaking change for Android.

Fixes:

• notifications not showing for Android Oreo when the app is not active
• notifications not showing for Android when the app is closed (neither in active, nor in inactive state)

Breaking changes

• Android callback function signature changed - message parameter is removed

// OLD
	pushPlugin.onMessageReceived(function callback(message, stringifiedData, fcmNotification) {
		var notificationBody = fcmNotification && fcmNotification.getBody();
        alert("Message received!\n" + notificationBody + "\n" + stringifiedData);
	});

// NEW
	pushPlugin.onMessageReceived(function callback(stringifiedData, fcmNotification) {
		var notificationBody = fcmNotification && fcmNotification.getBody();
        alert("Message received!\n" + notificationBody + "\n" + stringifiedData);
	});