added method to get both unblurred and blurred snapshots in an array

@smbarne I was wanting to get both a snapshot and blurred snapshot of a view without having to get a context or call drawViewHierarchyInRect twice in a row. In my case, this involves wanting to create a blur fade-in effect for a mapview where I can also hide the mapview once it has been snapshotted. 
But if you look at that method, you will see that it is also passing it into `UIGraphicsBeginImageContextWithOptions()`, so it could be eliminated as well. And in `RZBlurredImageInCurrentContext()`, in the other place where scale is needed, it is recalculated using `[[UIScreen mainScreen] scale]` anyway.