code: function readTxt(filePath, opts_, cb) {
    var parserOptions;
    if (typeof cb === 'undefined') {
      cb = opts_;
    } else {
      parserOptions = typeof opts_ === 'function' ? { map: opts_ } : opts_;
    }
    readData(filePath, { parser: parserTxt, parserOptions: parserOptions }, cb);
  }
docs: Asynchronously read a text file. Returns an empty string if file is empty.
  
  @function readTxt
  @param {String} filePath Input file path
  @param {Function|Object} [map] Optional map function or an object with `map` key that is a function. Takes the file read in as text and return the modified file. See example below.
  @param {Function} callback Has signature `(err, data)`
  
  @example
  io.readTxt('path/to/data.txt', function (err, data) {
  console.log(data) // string data
  })
  
  io.readTxt('path/to/data.txt', function (str) {
  return str.replace(/hello/g, 'goodbye') // Replace all instances of `"hello"` with `"goodbye"`
  }, function (err, data) {
  console.log(data) // string data with values replaced
  })