sass/postcss magic

gulpfile.js

var gulp = require('gulp');
var sass = require('gulp-sass');
var cssc = require('gulp-css-condense');
var postcss = require('gulp-postcss');
var pixrem = require('gulp-pixrem');

// Process Sass to CSS
gulp.task('sass', function () {
  return gulp.src('./sass/**/*.scss')
  .pipe(sass().on('error', sass.logError))
  .pipe(gulp.dest('./css'));
});

// PostCSS tasks, requires Sass to be completed first
gulp.task('postcss', ['sass'], function () {
  var processors = [
    require('postcss-merge-rules'),
    require('autoprefixer')({browsers: ['> 1%']}),
    require('csswring')
  ];

  return gulp.src('./css/**/*.css')
  .pipe(postcss(processors))
  .pipe(cssc())
  .pipe(pixrem('10px'))
  .pipe(gulp.dest('./css'));
});

// Watch for changes
gulp.task('default', function () {
  gulp.watch('./sass/**/*.scss', ['postcss']);
});