title: sequelize multiple foreign key includes only one column
body: <p>i have made two foreign keys from user table.</p>
  
  <pre><code>db.Subscription.belongsTo(db.User, {foreignKey: 'creatorId'});
  db.Subscription.belongsTo(db.User, {foreignKey: 'subscriberId'});
  </code></pre>
  
  <p>during search query i get <code>subscriberId</code> column included instead of <code>creatorId</code> </p>
  
  <pre><code>Subscription.findAll({
      where: {
        subscriberId: req.decoded._id
      },
      include: [
        {
            model: User, 
            foreignKey: 'creatorId', 
            attributes: ['name', 'role', 'uid', 'imageUrl']
        }
      ]
  })
  </code></pre>
  
  <p>can someone please find out what i am doing wrong here.  </p>