Add tests for include as child of a hierarchy

[overlookmotel]

This feature works, but would be good to have specific tests for it.

[leroydev]

Just to be sure I understand correctly, is this issue about validating that include is applied correctly to childs of the fetched model?

So for example:

this.folder.findAll({hierarchy: true, include: [{
  model: this.drive
}]).then(function(folders) {
  var folder = folders[0];
  expect(folder.children[0].drive).to.be.ok;
  expect(folder.children[0].drive.name).to.equal(this.drives.b.name);
});