Public check method for singleUse id

[MFlisar]

This would make it possible to return from a function before all the unnecessary builder stuff is done...

As retrieving the views, which may be useless if I don't want to show the Showcase afterwards...

[mengoni]

It would be very useful!

Is it possible to add this method to MaterialShowcaseView?

public static method hasFired(Context context, String showcaseID)