Update sass task

tasks/sass.js

@@ -1,21 +1,25 @@
 'use strict';
 
-var gulp = require('gulp'),
+const gulp = require('gulp'),
   autoprefixer = require('gulp-autoprefixer'),
   sass = require('gulp-sass'),
   rename = require('gulp-rename');
 
 function sassTask(options) {
-  gulp.task('sass', ['dupe'], function(){
+  // Requires: dupe.
+  gulp.task(
+    'sass',
+    gulp.series('dupe', function() {
       return options
         .src(options.workingDir + '/**/*.scss')
         .pipe(sass())
-      .pipe(autoprefixer({
+        .pipe(
-        browsers: ['last 5 versions']
+          autoprefixer()
-      }))
+        )
         .pipe(rename({ extname: '.css' }))
         .pipe(gulp.dest(options.workingDir));
-  });
+    })
+  );
 }
 
 module.exports = sassTask;