optipng vs pngquant

[moustacheful]

Hey, just tried using gulp-imagemin, but found some issues with usage.

1. Can't use pngquant, even though it's a dependency for imagemin.
2. When using pngquant (installing it on your own, which is a little redundant considering the previous point) you are forced to go through optipng, which is VERY slow, and doesn't necessarily translate to size reduction.

So, unless I'm missing something, shouldn't it be a flag between lossy:lossless which translates to using pngquant:optipng ?

[sindresorhus]

1. It's irrelevant what imagemin comes with. I've chosen to include the core lossless plugins that most will need in this plugin. You can easily add additional ones: https://github.com/sindresorhus/gulp-imagemin#use
2. Optipng is the best lossless PNG optimizer. It's not that slow for me, but depends on how the size of your PNGs and the optimizationLevel you select, and of course how slow your computer is.

That said. I have been planning to and going to look into making it more configurable. See #63