Fibonacci Iterator low completion rate

Fibbonacci Iterator has been hovering around 65% completion rate while still having a low attempt rate (~4), so I would like to try to improve on that.

My first thought is to expand the iteration protocol example to be less opaque. I found this part of my Julia journey quite frustrating due to the example given in [Julia's docs](https://docs.julialang.org/en/v1/manual/interfaces/) being so compact/limited that I feel it generalizes horribly (at least for those new to the concepts). I understand my viewpoint is biased to my experience and others might not find this as difficult, but that's why I'm pushing this idea first anyways.

I'd be happy to write up an expanded version of the iteration protocol example.

The only other thing that I can think of at the time is that the `instructions.md` are rather sparse (mostly just a title and single code sample) in comparison to our normal standards, so maybe this could be improved?

Any other thoughts?

In any case, the `instructions.md` has a smallproblem in that there is a second level heading `## Fibonacci Sequence` which is showing up as a task in the online editor, so this is a minor fix that needs to happen anyway.