docs(README.md): clarify current release and encourage use of master
ref(*): move ADD command to bottom

This effectively lets us cache the VOLUME, WORKDIR, EXPOSE, etc.
entries whenever we make changes to the components, speeding up local
development compilation.
Merge pull request #1502 from deis/optimize-builder

ref(*): move ADD command to bottom
Merge pull request #1572 from deis/doc-current-version

docs(README.md): clarify current release and encourage use of master
Merge branch 'master' into chore/new-init

Conflicts:
	builder/Dockerfile
	cache/Dockerfile
	database/Dockerfile
	logger/Dockerfile
	registry/Dockerfile
	router/Dockerfile