Update backbone-indexeddb.js
Update backbone-indexeddb.js

Fixes #23

Note that this adds an implicit dependency on jQuery.Deferred

```
var dfd = jQuery.Deferred();
```

Existing tests pass, and this works in my own project, but I've not created new tests that exercise these changes.
superfeedr/indexeddb-backbonejs-adapter,superfeedr/indexeddb-backbonejs-adapter,zawaideh/indexeddb-backbonejs-adapter,zawaideh/indexeddb-backbonejs-adapter