Added configuration for mypy

setup.cfg

 [tool:pytest]
 addopts = -v --cov flamenco_worker --cov-report term-missing --ignore node_modules -x
 
+[mypy]
+python_version = 3.5
+warn_unused_ignores = True
+ignore_missing_imports = True
+follow_imports = skip
+
 [pep8]
 max-line-length = 100