code: function _loadResponderList(responderListFilePath){
    var filePath = responderListFilePath;
  
    if(typeof filePath !== 'string'){
      return null;
    }
  
    if(!fs.existsSync(responderListFilePath)){
      throw new Error('File doesn\'t exist!');
    }
  
    if(!utils.isAbsolutePath(responderListFilePath)){
      filePath = path.join(process.cwd(), filePath);
    }
  
    return _loadFile(filePath);
  }
docs: Load the list file and return the list object
  
  @param {String} responderListFilePath
  @return {Array} responder list
  
  @api private