Twitter API 1.1 OAuth Get Use Data

I read this tutorial to implement twitter oauth in nodejs (for "login with twitter" purpose) - http://codetheory.in/how-to-use-twitter-oauth-with-node-oauth-in-your-node-js-express-application/

The last piece of code has this variable called results which is supposed to hold the user data sent back by twitter, but for me it only contains screen_name and user_id which is not enough. I need much more data like profile image, etc.

So I looked at the twitter documentation - https://dev.twitter.com/docs/api/1/get/users/show
The sample URL seems to work fine - https://api.twitter.com/1/users/show.json?screen_name=TwitterAPI&include_entities=true

But recently I read twitter will shut down API 1 soon and replace it with API 1.1

So I tried the 1.1 API - https://dev.twitter.com/docs/api/1.1/get/users/show
The sample URL does not work - https://api.twitter.com/1.1/users/show.json?screen_name=rsarver

Gives error -

{"errors":[{"message":"Bad Authentication data","code":215}]}

What am I doing wrong ? How do I get user info properly from twitter and hopefully in my Node.js code that uses this module - https://github.com/ciaranj/node-oauth ?

Thanks in advance!