3x2 Constrain Code needs fixing

[Diskprotek]

The option for 3x2 constrain are coded backwards. There is an easy fix in CropViewController.swift:

    let threeByTwo = UIAlertAction(title: "3 x 2", style: .default) { [unowned self] action in
        self.cropView?.cropAspectRatio = 2.0 / 3.0 **<-- This should be 3.0/2.0**
    }

I'd fix it myself, but I confess to not really knowing how GitHub works.