Use the One True Way for testing

Closes coop-cloud/abra#71.

Makefile

@@ -1,6 +1,6 @@
 .PHONY: test shellcheck docopt kcov codecov
 
-test_dind:
+test:
 	@sudo DOCKER_CONTEXT=default docker run \
 		-v $$(pwd):/workdir \
 		--privileged \
@@ -15,17 +15,6 @@ test_dind:
 	@DOCKER_CONTEXT=default docker stop abra-test-dind
 	@DOCKER_CONTEXT=default docker rm abra-test-dind
 
-test_docker:
-	@DOCKER_CONTEXT=default docker run \
-		-it \
-		--rm \
-		-v $$(pwd):/workdir \
-		decentral1se/docker-dind-bats-kcov \
-		sh -c "cd /workdir && bats /workdir/tests"
-
-test_local:
-	bats tests
-
 shellcheck:
 	@docker run \
 		-it \