Unions on nested objects return incorrect values ~13

[marshallswain]

var algebra = new set.Algebra( );
var union = algebra.union(
    {sort: {name: 1}},
    {sort: {name: 1}}
);

I would expect union to be

{
   "sort": {name: 1}
}

But it's coming back as

{
  "name": 1,
  "sort": {
    "name": 1
  }
}

I've set this test up, already, in this PR: #25