Laravel get a model collection ordered by a relation column

I'm trying to obtain a ranking table based on how much points that has an User.

My User model is (simplified):

namespace Gamify;
class User extends Model
{
    protected $table = 'users';

    public function points()
    {
        return $this->hasMany('Gamify\Point');
     }

     public function scopeMember($query)
     {
         return $query->where('role', '=', 'default');
     }
 }

And Point model is:

namespace Gamify;
class Point extends Model
{
    protected $table = 'points';

    protected $fillable = array(
        'points',
        'description'
    );

    public function user()
    {
        return $this->belongsTo('Gamify\User');
    }
}

I'd like to obtain a Collection of users with the sum of its points, ordered by this sum.

Something like this (this code is only a mockup):

public static function getRanking($limitTopUsers = 10)
{
    return User::member()->orderBy(sum('points'))->get();
}

I've been playing with User::with() and scopes and I'm trying not to use DB::raw().

Can anyone help me? Thanks in advance.

via Chebli Mohamed