function approveChanges () {
  console.log('Looks like there were some changes detected since last run.');
  backstop('approve', {
    config: {
      id: 'explicity_defined',
      paths: {
        bitmaps_reference: 'backstop_data/bitmaps_reference',
        bitmaps_test: 'backstop_data/bitmaps_test'
      }
    }
  });
}
run this to approve changes from the previous run.