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. 
since the scale needs to be retrieved for RZBlurredImageInCurrentContext method anyway I think it makes it less confusing to be sending the same scale variable to the context method as well.