16.4 Iterators has a flawed Fibonacci implementation

The iterator produces the following output
```
The first four terms of the Fibonacci sequence are: 
> 1
> 2
> 3
> 5
```
Usually [Fibonacci sequence](https://en.wikipedia.org/wiki/Fibonacci_number) is considered to start `[1,1,2,3]` or sometimes `[0,1,1,2]` but not `[1,2,3,5]`.