Use add facebook endpoint

- in facebook claim reward flow, always get a new auth token from the user (FB.login). if the user hasn't linked their fb account previously, link it and then claim. otherwise, update the auth token and then claim
- brings in bower component angular-facebook and deletes util/fb.js
- cleans up facebook-reward-controller.js, makes the functions promiseable
Why not just wrap ```Facebook.isReady();```?

```
$scope.facebookIsReady = function() {
  return Facebook.isReady();
}
```