Over a year's worth of corrections and improvements

Plus, a small example of custom iterators.

Thanks everyone for your contributions.

New chapter: Refactoring checklist

16.0.1

fix formatter panic

Various formatting issues and a little more commentary on fakes

Update working-without-mocks.md

The real insight, i think

Attempt to fix #598

This should fix the epub rendering in google play books

15.1.0

Add a tl;dr for the working without mocks chapter

New chapter: Working without mocks, stubs and spies

Plus some fixes from the community

Scaling acceptance tests (with light intro to gRPC)

14.0.0

Fix error in example

Various edits and fixes from the community

Thanks everyone

Little structural changes

13.0.2

little edits

Mention GOOS in acceptance tests intro

13.0.1

mention GOOS