Add Paeth to the list of supported prediction modes (#274)

nopaeth@2018-06-21T09:29:47.514Z -> paeth@2018-06-21T09:28:52.893Z

   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
-0.0962 | -0.4074 | -0.3002 |   0.0372 | -0.1525 | -0.0627 |    -0.0307