CSSNext

CSSNext is an amazing tool made by @MoOx and other guys from GitHub community. It's a PostCSS plugin that gives you possibility to use CSS features now, which are not supported by browsers yet. It has new set of great features. And what's most important, it's driven by W3C standards, and there is nothing more than specifications defined by W3C community.

You can see CSSNext all features on their website.