docs(docs.js): change deps array join to avoid orphan quotes

Change return value of docsApp.serviceFactory.prepareDefaultAppModule to include empty array `[]` instead of array containing one empty string element `['']`, for situations when the deps array is empty.

This will benefit plunkr/jsfiddle examples which lack animation or other dependencies, such as [ngChecked](http://docs.angularjs.org/api/ng.directive:ngChecked).

Current script.js sent to plunkr/jsfiddle when no deps exist: 
```javascript
angular.module('App', ['']);
```

New script.js sent to plunkr/jsfiddle when no deps exist:
```javascript
angular.module('App', []);
```