code: function addAttachment (docName, docRev) {
    const args = os.type() === 'Darwin' ? ['-l', '1'] : ['-b', '-n', '1']
    const stream = spawn('top', args).stdout
    const attName = `top-${Date.now()}.txt`
    const attContentType = 'text/plain'
    return db.addAttachment(dbName, docName, attName, docRev, attContentType, stream)
      .then(response => response.data.rev)
  }
docs: attach the output of 'top' to the document
  @param {String} docName
  @param {String} docRev
  @return {Promise} - fulfilled with new document revision