For fun, I took your original PNG from http://i.pi.gy/0K7d.png (205.5KB), converted it to maximum-quality JPEG (with Preview in OSX), then compressed it with JPEG Mini, resulting in a 122.6KB file.

ImageOptim was able to shave off an extra 10KB with no visible loss.

The resulting image at 112.2KB: https://i.imgur.com/kzZzfIi.jpg