login logic, reward model, and message model

Changes:

* The collector model is now accessible from app.collector after the user logs in.
* Additionally, all headers for any requests will automatically have the correct headers to make a valid request.
* Added reward model
* Added message model

Reward Models Usage:

```javascript
  var rewards = new RewardCollection('cat670022'); // rewardListing.json
  reward = rewards.get('prod123456'); // gets the partial reward detail that rewardListing gives.

  // To get the full one:
  reward.fetch(); // Grabs the full reward details

  // To get all the categories:
  var rewardCategories = new RewardCategoryModel();
  rewardCategories.fetch();
```

Message Model Usage:

```javascript
    var messages = new MessageCollection({max: 1, bucketId: 'mobileAppMessage'});
    messages.fetch(function() {  // request messages.json
        var message = messages.at(0); // Do something with the message
    });
```