eql(): fix wrong order of actual vs. expected

The helper `expect.eql()` function, like typical assertion methods,
takes `actual` then `expected`:

https://github.com/LearnBoost/expect.js/blob/master/expect.js#L850

But the `Assertion.prototype.eql` wrapper has been incorrectly
passing `this.obj` (the object being tested) as the `expected`, and
vice versa passing `obj` (the object used for comparison) as the
`actual`. This fixes that.