Set coverage threshold to 90%

.travis.yml

@@ -8,4 +8,5 @@ install:
 
 script:
   - make test
-  - make coverage
+  - make coverage_publish
+  - make coverage_report

Makefile

@@ -16,7 +16,14 @@ test:
 test_debug:
 	pipenv run python -m pytest -v --trace
 
-coverage:
+coverage_publish:
 	pipenv run python -m coveralls
 
-.PHONY: dependencies run debug test test_debug coverage
+coverage_report:
+	pipenv run python -m coverage report --fail-under 90
+
+clean:
+	pipenv run python -m coverage erase
+	rm -rf .pytest_cache .cache
+
+.PHONY: dependencies run debug test test_debug coverage_publish coverage_report clean