Improving the section on the Fold pattern

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It has come up in the issues section before that the chapter on the Fold pattern is fairly confusing (see issue #54).
A question about the same thing came up recently in URLO, in this thread.
As an answer to that question, I wrote a semi-long answer, describing:

1. Iterator::fold as a simple left-fold example
2. A Foldable trait which has the FP sense (Haskell sense to be specific) of a generic right-fold.
3. An implementation of the Foldable trait on a BinaryTree which performs a depth-first traversal from right to left.

I would like to port this answer to the chapter on Fold. Are there some other things you would like to see in the chapter? Or maybe you want me to remove something?