Assertion error does not state problematic parts for Maps

```
chai.expect(new Map([['a','a']])).to.deep.equal(new Map([['a','b']]))
// AssertionError: expected {} to deeply equal {}
chai.expect([['a','a']]).to.deep.equal([['a','b']])
// AssertionError: expected [ [ 'a', 'a' ] ] to deeply equal [ [ 'a', 'b' ] ]
```

As you can se it is not clear why it fails from the error message