Change numbering to be from 1 (not 0)

Although it was natural to use 0 as numbering, when reviewing this to practice
explaining, I would keep making the same mistake and jumping to 1. Let's just
renumber to keep it simple.
Merge pull request #21 from glenjarvis/refactor/renumber_iterative_examples

Change numbering to be from 1 (not 0)