title: Nested relations with Sequelize
body: <p>I am using Sequelize with Node + MySQL.</p>
  
  <p>I have a model structure similar to this:</p>
  
  <pre class="lang-js prettyprint-override"><code>// models:
  var Group, Issue, Invite;
  
  // many Issues per Group
  Group.hasMany(Issue);
  Issue.belongsTo(Group);
  
  // Groups can invite other Groups to work on their Issues
  Issue.hasMany(Invite, {foreignKey: groupId});
  Invite.belongsTo(Issue, {foreignKey: groupId});
  Group.hasMany(Invite, {foreignKey: inviteeId});
  Invite.belongsTo(Group, {foreignKey: inviteeId});
  
  // given an Issue id, include all Invites + invited Groups (inviteeId) - But how?
  var query = {
      where: {id: ...}, 
      include: ???
  };
  Issue.find(query).complete(function(err, issue) {
      var invites = issue.invites;
      var firstInvitedGroup = issue.invites[0].group;
      // ...
  });
  </code></pre>
  
  <p>Is this at all possible? What are possible work-arounds? Thank you!</p>