Generating sprites with percentage position

[vgavro]

I don't see scripts that is used for sprites/css generation, there is scripts in 2.2.7 tag, but not for version 3 as I could find. Actually I want to generate css classes based on percentage instead of fixed position, as related issues is fixed already in google chrome? (or not?) There is related tickets joypixels/emojione#243 joypixels/emojione#220
Anyway, have build scripts in open source (as for 2 version) would be great. Thanks!