The README doesn't mention which browsers it supports (presumably at least the Chrome/Firefox/Edge evergreens?). I would add that, and perhaps a comparison of sizes between this and Normalize.css.
Until that is done: It supports IE11, FF48+, Edge and Chrome. Mobile browser tests are on the way. Some things are ported from Normalize.css for backword compatibility, but the goal is to remove them as soon as IE11 drops below 1%.