code: function sanitizeBucketName(bucketName) {
      return _(bucketName)
          .split('.')
          .filter(e => e)
          .map(_.toLower)
          .map(e => _.replace(e, '_', '-'))
          .join('.');
  }
docs: Sanitize the bucketName following the rule found here:
  http://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-s3-bucket-naming-requirements.html
  @param bucketName
  @returns {string}