Implement reference comparison

[jakubzitny]

This MR adds referenceEqual BDD method and referenceEqual and referenceNotEqual TDD methods according to the discussion in #210.

Close #210.

[jakubzitny]

I am not sure how you generate the README examples, should I just manually copy the comments from the implementation to README.md @astorije?

[jankuca]

@jakubzitny Will expect().to.not.referenceEqual() work?

[jakubzitny]

Yes, it's already in the test cases: https://github.com/astorije/chai-immutable/pull/218/files#diff-c1129c8b045390789fa8ff62f2c6b4a9. The to.nots and not.tos and similar chaining calls are handled by chai out of the box in the BDD API.

[astorije]

I am not sure how you generate the README examples, should I just manually copy the comments from the implementation to README.md @astorije?

Yup, it's a very complex build step that involves copying and pasting 😅
Thanks for opening this, @jakubzitny, that's awesome, I'll be looking into your PR very shortly (and if I don't, it's because I dropped the ball and feel free to ping me!)

[astorije]

@jakubzitny, I took the liberty to add the doc in the README, and also renaming referenceNotEqual into notReferenceEqual and editing the examples a little to make them pass tests.
How do you feel about those changes? It's pretty late here so I'll let you double-check me before merging 😅

[astorije]

Thanks a lot for your help!! 🙏

[jakubzitny]

Changes are OK. The commit messages could be better, but that's your call 😉 I can squash the notReferenceEqual to my implementation commit if you want. Or we can just merge it as it is, again your call 🙂

[astorije]

Heh, that's fine for this one.
Thank you very much for your help!

[astorije]

This has now be released as part of v2.1.0. Thanks again!