CSS module support, @extend support, and more

[rstacruz]

You'll now be able to apply modular scale font sizes using CSS modules!

.myButton {
  composes: msFontSize2 from 'responsive-modular-scale.css/modularscale.module.css';
}

You can also use responsive-modular-scale as functional selectors (aka @extend):

.myButton {
  @extend %ms-font-size-2;
}

Lots of changes here - this is a full rewrite.