Update Twitter avatar with Apps Script

gistfile1.js

function oAuthConfig() {
  var oAuthConfig = UrlFetchApp.addOAuthService("twitter");
  oAuthConfig.setAccessTokenUrl("http://api.twitter.com/oauth/access_token");
  oAuthConfig.setRequestTokenUrl("http://api.twitter.com/oauth/request_token");
  oAuthConfig.setAuthorizationUrl("http://api.twitter.com/oauth/authorize");

  // Register an app at https://dev.twitter.com/apps/new to get the following key and secret
  oAuthConfig.setConsumerKey("PUT CONSUMER KEY HERE");
  oAuthConfig.setConsumerSecret("PUT CONSUMER SECRET HERE");
}

function setProfileImage() {

  oAuthConfig();

  // This is a picture that will be set as Twitter avatar
  var picture = UrlFetchApp.fetch("https://twitter.com/images/resources/twitter-bird-white-on-blue.png");
  var encodedImage = Utilities.base64Encode(picture.getContent());
  var options =
  {
    "method": "post",
    "oAuthServiceName" : "twitter",
    "oAuthUseToken" : "always",
    "payload": { "image" : encodedImage, "skip_status": true}
  };
  var request = UrlFetchApp.fetch("http://api.twitter.com/1/account/update_profile_image.json", options);
}