secret option doesn't seem to do anything

[kasperpeulen]

Thanks for making this package, it works great, only I can't get this secret option to work.

For example, see this gist:
https://gist.github.com/kasperpeulen/4c25527ae51e41c8d2ef

import 'package:github/server.dart';
import 'package:prompt/prompt.dart';

main() async {

  String username = askSync(new Question('Github Username'));
  String password = askSync(new Question('Github Password', secret: true));

  Authentication auth = new Authentication.basic(username, password);
  GitHub gitHub = createGitHubClient(auth: auth);

  // creates a gist with a README.md file
  Gist gist = await gitHub.gists.createGist({
    "README.md" : "Hello world!"
  }, description: "Hello world", public: true);

  print('Gist created at ${gist.htmlUrl}');
}

It looks for me like this: