Update AnalysisService for UMD national+subnational

Yo dudes, this PR updates AnalysisService to give UMD national+subnational results.

Note that it's now totally async, so when you execute a request you pass in callback functions for onSuccess and onFailure. So, just inject `services/AnalysisService` for an instance when you need it and boom. Example:

```javascript
var config = {dataset: 'umd-loss-gain', iso: 'bra', thresh: 10};
var success = function(data) {console.log('boom', data)};
var failure = function(responseText, status, error) {console.log('oops', responseText);};
service.execute(config, success, failure);
```

For the above example, it's hitting this API endpoint under the hood:
http://beta.gfw-apis.appspot.com/forest-change/umd-loss-gain/admin/bra?thresh=75

All tests are passing in the AnalysisService Suite. :D