code: function sass() {
    return gulp.src('src/assets/scss/app.scss')
      .pipe($.if(!PRODUCTION, $.sourcemaps.init()))
      .pipe($.sass({
        includePaths: ['node_modules/foundation-emails/scss']
      }).on('error', $.sass.logError))
      .pipe($.if(PRODUCTION, $.uncss(
        {
          html: ['dist/**/*.html']
        })))
      .pipe($.if(!PRODUCTION, $.sourcemaps.write()))
      .pipe(gulp.dest('dist/css'));
  }
docs: Compile Sass into CSS