Show Nim: New Pixie 5.0 release with significant performance improvements

[guzba]

PNG encoding can certainly be further optimized for file size, but I am not a 
fan of the approach taken by TinyPNG. It uses lossy compression which is very 
strange in the context of PNG, which is a form of lossless compression. I would 
much rather keep PNG as a lossless encoder and someday have a JPEG encoder for 
the lossy encoding.