title: projection not working with db.collection.find in mongo
body: <p>I have started to use mongodb just a day back and have encountered an issue.
  I searched on net and stackoverflow for how to hide _id value in final answer and following the answers provided I tried to get my code run but still the _id part shows.</p>
  
  <p>P.S.: I am using cloud9 as the ide.</p>
  
  <pre><code>var mongo = require('mongodb').MongoClient;
  mongo.connect('mongodb://localhost:27017/learnyoumongo', function(err, database) {
          if(err) throw err;
          const db = database.db('learnyoumongo');
          var parrots = db.collection('parrots');
          parrots.find({
              age: { $gt: +process.argv[2] }
          },{
              name: 1,
              age: 1,
              _id: 0
          }).toArray(function(err, docs){
              if(err) throw err;
              console.log(docs);
              database.close();
          });
  });
  </code></pre>