Adds extensions to Image and Color that allow user to grab a color at a specified pixel in an image

Image+ColorAt.swift

public extension Image {
    public func color(at point: Point) -> Color {
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue)

        guard let offscreenContext = CGContext(data: nil, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 0, space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: bitmapInfo.rawValue) else {
            print("Could not create offscreenContext")
            return clear
        }

        offscreenContext.translateBy(x: CGFloat(-point.x), y: CGFloat(-point.y))

        layer?.render(in: offscreenContext)

        guard let pixelImage = offscreenContext.makeImage() else {
            print("Could not create pixel image")
            return clear
        }
        return Color(Image(cgimage:pixelImage))
    }
}

public extension Color {
    ///  Initializes and returns a new Color object made up of a repeating pattern based on a specified Image.
    ///  ````
    ///  let p = Color("pattern")
    ///  ````
    /// - parameter pattern: a String, the name of an image to use as a pattern.
    public convenience init(_ patternImage: Image) {
        let uiim = patternImage.uiimage
        self.init(UIColor(patternImage: uiim))
    }
}