Expose functions of UIImage for getting color of pixel at point

[zakkhoyt]

// A one line call to retrieve color of a pixel public func pixelColorAt(point: CGPoint) -> UIColor?

// UIImage to pixel buffer in one line call public func pixelBuffer() -> CVPixelBuffer public func pixelBuffer() -> (pixelBuffer: CVPixelBuffer, size:CGSize, bytesPerRow: CGFloat)

Also add class function variants

[zakkhoyt]

I added the following public class methods:

    public class func pixelBufferOf(image: UIImage) -> CVPixelBuffer? 
    public class func pixelBufferPropertiesOf(image: UIImage) -> (pixelBuffer: CVPixelBuffer?, size:CGSize, bytesPerRow: Int) 
    public class func getSizeOf(pixelBuffer: CVPixelBuffer) -> CGSize 
    public class func getBytesPerRowOf(pixelBuffer: CVPixelBuffer) -> Int
    public class func pixelColorOf(image: UIImage, at point: CGPoint) -> UIColor? 

and their matching instance methods

public func pixelBuffer() -> CVPixelBuffer? {
public func pixelColorAt(point: CGPoint) -> UIColor? {
public func pixelBufferProperties() -> (pixelBuffer: CVPixelBuffer?, size:CGSize, bytesPerRow: Int) {