RangeError when comparing two objects with eql

I'd like to use `eql` to compare two objects:

```
expect(tokenizeTagText(text)).to.eql([new TextField('only text field')]);
```

But I get this using `mocha`:

```
RangeError: Maximum call stack size exceeded
```

However, if I change the test to use `equal`, they look the same:

```
Error: expected [ { name: 'only text field',
markup: { '0': , length: 1 } } ] to equal [ { name: 'only text field',
markup: { '0': , length: 1 } } ]
```

It seems the `RangeError` comes from expect.js.

It seems the issue is with comparing jQuery elements:

```
it('failing', function () {
expect([ { name: 'only text field',
markup: { '0': $(''), length: 1 } } ]).to.eql([ { name: 'only text field',
markup: { '0': $(''), length: 1 } } ]);
});
it('successful', function () {
expect([ { name: 'only text field',
markup: { '0': '', length: 1 } } ]).to.eql([ { name: 'only text field',
markup: { '0': '', length: 1 } } ]);
});
```

Start by running the two minimal mocha examples in the issue, comparing eql on objects containing jQuery elements with the string-based successful case. Trace the eql comparison until it recurses into the jQuery object; done means the jQuery case no longer raises a maximum call stack error and the existing comparisons still pass.

Written by the indexing model from the issue text.