v1.0.0-rc14

This release introduces mozjpeg and pngquant, which offer much smaller file sizes for jpeg and png images respectively, albeit with increased CPU usage during encoding.

These can be used via encoder presets:

encode_preset: {
"pngquant" : { quality: [min number, max number], speed: [number]},
"mozjpeg": { quality: number, progressive: bool}
}