Misaligned feature's overlay

[eugeniobaglieri]

FIx a bug that cause misaligned overlay, if the preview layer has not the screen size.
I think that also ImageCapturer.swift at line 51 should be modified in the same way, maybe adding a sourceSize parameter in the function.

let processed: CIImage
    if let feature = feature {
        let normalized = feature.normalized(source: UIScreen.main.bounds.size, 
                                            target: image.extent.size)