old_contents: var gulp     = require('gulp');
  var sequence = require('gulp-sequence');
  var del      = require('del');
  var bundler  = require('../lib');
  
  gulp.task('default', sequence('clean', 'js:watch'));
  
  gulp.task('clean', function () {
    return del('dist');
  });
  
  const src = 'index.js'
  
  gulp.task('js', function () {
    return bundler(src);
  });
  gulp.task('js:watch', function () {
    return bundler(src);
  });
  
new_contents: var gulp     = require('gulp')
  var sequence = require('gulp-sequence')
  var del      = require('del')
  var bundler  = require('../lib')
  
  gulp.task('default', sequence('clean', 'js:watch'))
  gulp.task('build', sequence('clean', 'js'))
  
  gulp.task('clean', function () {
    return del('dist')
  })
  
  const src = 'src/index.js'
  
  gulp.task('js', function () {
    return bundler(src)
  })
  gulp.task('js:watch', function () {
    return bundler(src, {watch: true})
  })
  
subject: update adding build task