Lint more files, relax some type checks (#43)

tox.ini

@@ -22,11 +22,11 @@ changedir =
 commands =
 ; Prefer putting everything in one pylint command to profit from duplication
 ; warnings.
-  py37-lint: pylint opentelemetry-api/src/opentelemetry/ opentelemetry-api/tests/
+  py37-lint: pylint opentelemetry-api/src/opentelemetry/ opentelemetry-api/tests/ opentelemetry-api/setup.py
   py37-mypy: mypy opentelemetry-api/src/opentelemetry/
-; For test code, we don't want to use the full mypy strictness, so we use its
-; default flags instead.
-  py37-mypy: mypy opentelemetry-api/tests/ --config-file=
+; For test code, we don't want to enforce the full mypy strictness
+  py37-mypy: mypy opentelemetry-api/src/opentelemetry/
+  py37-mypy: mypy --config-file=mypy-relaxed.ini opentelemetry-api/tests/ opentelemetry-api/setup.py
   test: python -m unittest discover
 
 [testenv:docs]