Add a cautionary note about OOP

[chillenzer]

Code design based heavily on inheritance has become a bit unfashionable over the years. One of its pitfalls is that code-wise sensible abstractions are not necessarily related to real-world ones. Examples: Is a Square a special case (translating to child class) of a Rectangle or the other way round? Is a Penguin a Bird or a Fish? I would suggest that we add a challenge (or even a section) about this at the end of the inheritance chapter.

Likely related to #14.

[edbennett]

We also try and touch on this in the final episode; do you think this could be included in that discussion, or does it want a separate mention earlier in the lesson?

[chillenzer]

I'm not there yet. Update once I've read it. (Sorry, I've checked the chapter titles and from that it wasn't obvious that it would appear again later.)

[chillenzer]

Oh, nice! Just stumbled across the "Squares" example in the Decorators chapter. That is a nice implementation to contrast with the inheritance-based version.