Configure mypy and flake8 for our re-export files

This removes the need to use __all__ in these files, while also
allowing us to have strictness elsewhere in the codebase.

.travis.yml

@@ -30,8 +30,7 @@ matrix:
       install:
         - 'pip install .[qa]'
       script:
-        # Ignore F401, which are unused imports. flake8 is a primitive tool and is sometimes wrong.
-        - 'flake8 --extend-ignore F401 jedi setup.py'
+        - 'flake8 jedi setup.py'
         - 'mypy jedi sith.py'
 install:
     - sudo apt-get -y install python3-venv