Set equality is unexpectedly ordered

```
  it('Compares sets correctly.', (done) => {
    expect(new Set(['a', 'b'])).toEqual(new Set(['b', 'a']));
    done();
  });
```

```
      Error: Expected Set (2) {'a', 'b'} to equal Set (2) {'b', 'a'}
      + expected - actual

      -["a","b"]
      +["b","a"]
```

This is with 1.18.0. I expect set equality to be independent of order; the order of elements is an implementation detail.
