gulpfile.js

var gulp         = require('gulp');
var autoprefixer = require('gulp-autoprefixer');
var browserSync  = require('browser-sync');
var concat       = require('gulp-concat');
var filter       = require('gulp-filter');
var jshint       = require('gulp-jshint');
var minifycss    = require('gulp-minify-css');
var newer        = require('gulp-newer');
var notify       = require('gulp-notify');
var plumber      = require('gulp-plumber');
var reload       = browserSync.reload;
var sass         = require('gulp-sass');

var onError = function(err) {
  notify.onError({
    title:    "Error",
    message:  "<%= error %>",
  })(err);
  this.emit('end');
};

var plumberOptions = {
  errorHandler: onError,
};

gulp.task('minifycss', function() {
  return gulp.src('assets/css/**/*.css')
    .pipe(minifycss())
    .pipe(gulp.dest('assets/css'))
});

gulp.task('sass', function() {
  var autoprefixerOptions = {
    browsers: ['last 2 versions'],
  };

  var filterOptions = '**/*.css';

  var reloadOptions = {
    stream: true,
  };

  var sassOptions = {
    includePaths: [
      'bower_components/bourbon/app/assets/stylesheets',
      'bower_components/mq-sass/stylesheets'
    ]
  };

  return gulp.src('assets/sass/**/*.scss')
    .pipe(plumber(plumberOptions))
    .pipe(sass(sassOptions))
    .pipe(autoprefixer(autoprefixerOptions))
    .pipe(gulp.dest('assets/css'))
    .pipe(filter(filterOptions))
    .pipe(reload(reloadOptions));
});

gulp.task('watch', function() {
  gulp.watch('assets/sass/**/*.scss', ['sass']);
});

gulp.task('browsersync', function() {
  browserSync({
    server: {
      baseDir: './'
    },
    open: false,
    online: false,
    notify: false,
  });
});

gulp.task('build', ['sass']);
gulp.task('default', ['sass', 'browsersync', 'watch']);
gulp.task('production', ['build'], function() {
  gulp.start('minifycss');
});