Reduce the scope of the prologue.

This reduces the story being told in the prologue and relegates it to a
practice chapter at the end of the document.
Change Part 1 to theory.

Using the Art of Agile Development (needs citation), we revamp the first
part to be a quick overview of how to develop which we'll build cloud on
in later practice chapters.
Update Part 3 with Margarine specifics.

The updated part 3 is a practice part that uses Margarine to show the
items learned in the first two parts.