add shellspec golden harness for the legacy make engine

- spec/golden/cases.txt: 69 black-box cases (CLI wrapper mode and make
  include mode) run in a hermetic sandbox with a mocked docker
- spec/golden/expected/*.txt recorded from this engine (baseline)
- make test / test-golden / golden-record / lint dev targets

spec/fixtures/host-project/stack/host/host.mk

@@ -0,0 +1,10 @@
+# Stack host: consul + fabio (80/443) + registrator, one instance per host.
+host                            ?= host/consul host/fabio host/registrator
+
+.PHONY: host
+host:
+	$(call make,up STACK="$(host)")
+
+.PHONY: host-down
+host-down:
+	$(call make,down STACK="$(host)")