hoodie.task.start should progress with task object

it currently progresses with something like

```js
hoodie.taks.start('test', {}).progress(function(task) {
  // task should be task object with id, type, createdAt etc, but instead is something like
  // {
  //   id: 'org.couchdb.user:user_anonymous/xpyjy50',
  //   rev: '1-72a0f32b32719bca8db387d9e3340184',
  //   ok: true
  // }
});
```