Reworking chapter 2 build to fit canonical builds better.

This reflects the build at the end of the "pulling it all together" section
that's being added to chapter 2.
Updates based on writing, and to sbt 0.13.0-M2
Merge pull request #1 from jsuereth/wip/jsuereth-chapter2-rework-canonical-build

Wip/jsuereth chapter2 rework canonical build