title: JSON stringify converts 0 to null
body: <p>I am trying to convert my object to JSON but it doesn't convert my enum to 0. When I print the enum I get 0 but when I use inside the object it becomes null. If I use string, instead of integer it works.</p>
  
  <pre><code>(function () {
      'use strict';
      var ItemStatus = {
          'Prepared': 0,
          'Ongoing': 1,
          'Finished': 2
      };
      module.exports = ItemStatus;
  })();
  
  (function () {
      'use strict';
      var ItemStatus = require('./itemstatus');
  
      function ItemDetail(detail) {
          detail = detail || {};
  
          this.message = detail.message || null;
          this.location = detail.location || null;
          this.status = detail.status || null;
          this.date = detail.date || null;
  
      }
  
      module.exports = ItemDetail;
  })();
  
  (function () {
      'use strict';
  
      var ItemDetail = require('./itemdetail');
      var ItemStatus = require('./itemstatus');
  
      function Item(item) {
  
          item = item || {}
  
          this.name = item.name || null;
          this.details = item.details || [];
          this.isFinished = item.isFinished || null;
          this.finishDate = item.finishDate || null;
  
      }
  
      Item.prototype.addDetail = function(message, location,date,status) {
  
          if (this.isFinished) {
              this.isFinished = false;
          }
  
          console.log('Status: ' + status); //Prints 0 correctly
          var detail = new ItemDetail({
              message: message,
              location: location,
              date:date,
              status:status
  
          });
  
          this.details.push(detail);
          if (status === ItemStatus.Finished) {
              this.isFinished = true;
              this.finishDate = date;
          }
      };
  
  
      module.exports = Item;
  })();
  </code></pre>
  
  <p>Failing Test</p>
  
  <pre><code>var should = require('should');
  
  var Item = require('../lib/models/item');
  var ItemDetail = require('../lib/models/itemdetail');
  var ItemStatus = require('../lib/models/itemstatus');
  
  
  describe('Item Detail Test:', function() {
     this.enableTimeouts(false);
  
  
      var myItem = new Item({
          name: 'Something',
      });
  
      myItem.addDetail('Something happened','NY',1212122,ItemStatus.Prepared);
      myItem.addDetail('Another thing','NY',1412122,ItemStatus.Ongoing);
      myItem.addDetail('It is done','NY',1212122,ItemStatus.Finished);
  
  
      it('should print JSON', function() {
          myItem.name.should.eql('Something');
          console.log(myItem.details[0].status);
          myItem.details[0].status.should.eql(ItemStatus.Prepared);
          console.log(JSON.stringify(myItem));
      });
  });
  </code></pre>
  
  <p>When printed my Item shows the following</p>
  
  <pre><code>{"name":"Something","details":[{"message":"Something happened","location":"NY","status":null,"date":1212122},{"message":"Another thing","location":"NY","status":1,"date":1412122},{"message":"It is done","location":"NY","status":2,"date":1212122}],"isFinished":true,"finishDate":1212122}
  </code></pre>