Ray Wenderlich's UIImage serializer for Alamofire, updated for Alamofire 2.0 and Swift 2

Alamofire+UIImage.swift

extension Alamofire.Request {
	
	/** Response serializer for images from: http://www.raywenderlich.com/85080/beginning-alamofire-tutorial */
	class func imageResponseSerializer() -> GenericResponseSerializer<UIImage> {
		return GenericResponseSerializer { request, response, data in
			
			guard let validData = data else {
				let failureReason = "Data could not be serialized. Input data was nil."
				let error = Error.errorWithCode(.DataSerializationFailed, failureReason: failureReason)
				return .Failure(data, error)
			}
			
			if let image = UIImage(data: validData, scale: UIScreen.mainScreen().scale) {
				return Result<UIImage>.Success(image)
			}
			else {
				return .Failure(data, Error.errorWithCode(.DataSerializationFailed, failureReason: "Unable to create image."))
			}

		}
	}
 
	/** Convenience method for returning images from: http://www.raywenderlich.com/85080/beginning-alamofire-tutorial */
	func responseImage(completionHandler: (NSURLRequest?, NSHTTPURLResponse?, Result<UIImage>) -> Void) -> Self {
		return response(responseSerializer: Request.imageResponseSerializer(), completionHandler: completionHandler)
	}
}