new doTweet function

botcode.gs

function doTweet (tweet) {
  var service = getTwitterService();
  if (service.hasAccess()) {
    var payload = {"status" : tweet }
  } else {
    var authorizationUrl = service.authorize();
    msgPopUp('<p>Please visit the following URL and then re-run "Send a Test Tweet": <br/> <a target="_blank" href="' + authorizationUrl + '">' + authorizationUrl + '</a></p>');
  }

  var parameters = {
    method: 'post',
    payload : payload
  };
  try {
    var result = service.fetch('https://api.twitter.com/1.1/statuses/update.json', parameters);
    Logger.log(result.getContentText());    
  }  
  catch (e) {    
    Logger.log(e.toString());
  }
}