update readme - we now use pngcrush
remove unused dependency on HughesPJClass
clean up shaders/filter.frag a bit
switch back to optipng + pngcp for compression

Revert "use pngcrush instead of pngcp + optipng"
This reverts commit 04901eedd7ffde8be0dd5007ec6495e82e8d9221.

Revert "update readme - we now use pngcrush"
This reverts commit a8a3268c63acee1c3b9f9768f61030b42938bb5c.
optimize loader some more
update stars to use fixed canvas resolution
pack the burst SVG more efficiently