Add Makefile for CI targets.

Makefile

+PIPENV := pipenv run
+
+apply-isort:
+	@$(PIPENV) isort \
+	--recursive \
+	--apply \
+	--settings-path=setup.cfg
+.PHONY: apply-isort
+
+isort:
+	@$(PIPENV) isort \
+	--quiet \
+	--recursive \
+	--check-only \
+	--diff \
+	--settings-path=setup.cfg
+.PHONY: isort
+
+pylava:
+	@ls -d */ | xargs $(PIPENV) pylava
+.PHONY: pylava
+
+checks:
+	$(PIPENV) python manage.py check
+	$(PIPENV) python manage.py makemigrations --check
+.PHONY: checks
+
+style: isort pylava
+.PHONY: style
+
+test:
+	$(PIPENV) pytest -v --cov
+.PHONY: test
+
+gitlab-ci: checks style test
+.PHONY: gitlab-ci