Set comparison with eql is wrong

[robbie-c]

expect(new Set([1])).not.to.be.eql(new Set([2])); // fails

You get the following output:
Error: expected {} to sort of not equal {}
Expected :{}
Actual :{}

I can work on a PR for this.

[robbie-c]

Create PR #144

[EvanHahn]

I forked this project and created expecting.js. It has support for Sets, if you're interested.

Hope this can help!