Change to new version of pngjs
Change to new version of pngjs

They removed the `node-zlib-backport` dependency yesterday:
https://github.com/lukeapage/pngjs/commit/b914ab4d80add0844cfaec663a9f4f7cbaaca860

You should now be able to depend on their latest version.
oliver-moran/jimp,oliver-moran/jimp,neophob/jimp,skoa-h/jimp,oliver-moran/jimp,neophob/jimp,neophob/jimp,skoa-h/jimp,skoa-h/jimp