Wire up a mocked appDirectives.js

I'm learning Angular so keep that in mind but it seems that the directives file should be mocked and wired up in the app already just as services and controllers are. For example:

```
// index.html
<script src="js/appDirectives.js"></script>

// appDirectives.js
angular.module('MainDirectives', []).directive('example', function(){

});

// app.js
'MainDirectives'
```
