Add tab ID to 'tabs_get' method response

As discussed in issue #114 this fix will add the tab ID to the response object when not specifying a tab.

![breach-tabs-ids](https://cloud.githubusercontent.com/assets/945367/3620485/12d0c5d0-0e01-11e4-9b5a-68e5c2376164.png)

The screenshot above demonstrates the ID in action using the following snippet to get and log each tab.

```javascript
breach.module('core').call('tabs_get', {}, function(err, res) {
  res.forEach(function(tab) {
    console.log(tab);
  });
});
```