code: function buildCsrSubject (commonName, options) {
    var subject = '/CN=' + commonName
    Object.keys(SUBJECT_ATTRIBUTES).forEach(function (key) {
      if (options[key]) {
        subject = subject + '/' + SUBJECT_ATTRIBUTES[key].name + '=' +
          options[key]
      }
    })
    return subject
  }
docs: Convert the X509 subject attributes specified on the command-line into a
  flat X509 subject string for use with openssl commands.
  @param {String} commonName - The X509 Common Name (CN) specified on the
  command line.
  @param {Object} [options] - Options to use in generating the CSR and private
  key.
  @returns {String} The X509 Subject in openssl display format.