EDIT: Updated based on info from comments
The style of request is quite different between logging in to get a token and the subsequent requests:
For login
The docs specify that login actions must be done with a POST request to /api/login/ with a body that contains username or email and password as url-encoded params
var request = require('request');
var url = 'http://localhost:3000/api/v1/login/'
var user = 'test35';
var pass = 'mypassword';
// Save these for future requests
var userId;
var authToken;
// Use POST instead of GET
request.post(
  {
    uri: url,
    // I'm using form because it matches the urlEncoding behaviour expected by `restivus`
    form: { username: user, password: pass }
  },
  function(err, httpResponse, body) {
    if (err) {
      return console.error('post failed:', err);
    }
    var json = JSON.parse(body);
    authToken = json.data.authToken;
    userId = json.data.userId;
    console.log('Post successful!  Server responded with:', body);
  }
);
For future requests
Now you need to set the correct headers with the previously saved userId and authToken
According to the docs, that means X-User-Id and X-Auth-Token headers on all subsequent requests
var request = require('request');
var url = 'http://localhost:3000/api/v1/articles/'
request.get({
  uri: url, 
  headers: {
    'X-User-Id': userId,
    'X-Auth-Token': authToken
  }
}, function(err, httpResponse, body) {
  if (err) {
    return console.error('get failed:', err);
  }
  console.log('Get successful!  Server responded with:', body);
});
Putting it together:
We want to make sure we get the authToken before making any further requests. 
This means making the second request in the callback of the first function like so:
var request = require('request');
var url = 'http://localhost:3000/api/v1/login/';
var user = 'test35';
var pass = 'mypassword';
// Save these for future requests
var userId;
var authToken;
// Use POST instead of GET
request.post(
  {
    uri: url,
    // I'm using form because it matches the urlEncoding behaviour expected by `restivus`
    form: { username: user, password: pass }
  },
  function(err, httpResponse, body) {
    if (err) {
      return console.error('post failed:', err);
    }
    var json = JSON.parse(body);
    authToken = json.data.authToken;
    userId = json.data.userId;
    console.log('Post successful!  Server responded with:', body);
    // And now we make the second request
    // Welcome to callback hell
    var articlesUrl = 'http://localhost:3000/api/v1/articles/';
    request.get({
      uri: articlesUrl, 
      headers: {
        'X-User-Id': userId,
        'X-Auth-Token': authToken
      }
    }, function(err, httpResponse, body) {
      if (err) {
        return console.error('post failed:', err);
      }
      console.log('Get successful!  Server responded with:', body);
    });
  }
);