Find users by group

Heyho, 
Thanks for your package! Is there a way to receive all users by a group?

Something like:

  ```
   public function scopeInsideGroup($query, $group = 'default')
    {
        return $query->whereHas('roles', function ($relation_query) use($group) {
            $relation_query->where('group', '=', $group);
        });
    }
```

Cheers,
Stan