code: function pcss(styles) {
      var done = false;
      var res;
  
      postcss([cssnext()])
        .process(styles, { from: undefined })
        .then(function(next) {
          done = true;
          res = next;
        });
  
      deasync.loopWhile(function() {
        return !done;
      });
  
      return res;
    }
docs: sync pcss