[BugFix] Collection.php

To enable Lazy Eager Loading with Constraints.

When I now use something like this it fails:

```php
$users = User::all();
$users->load(array('posts' => function($query)
{
$query->where('title', 'like', '%first%');
}))->get();
```

The problem I think is the handling with func_get_args(), it puts the relations array into another array.