Allow modules to load their own dependencies

Just testing the waters here.

Let's say our application has 3 modules A, B, and C. Module B depends on modules C, D, and E.

```
A
B -> C, D, E
C
```

But in our `application.config.php` we only specify A, B, and C.

```php
return array(
    'modules' => array(
        'A',
        'B',
        'C',
    ),
);
```

This little patch will allow B to load its dependencies D and E without having the user to specify it in their `application.config.php`.

```php
namespace B;

use Zend\ModuleManager\ModuleManager;

class Module
{
    public function init(ModuleManager $modules)
    {
        $modules->loadModule('C');
        $modules->loadModule('D');
        $modules->loadModule('E');
    }
}
```