Fix tox job directory name

tox.ini

@@ -39,7 +39,7 @@ commands =
     black: {envpython} -m black --check --diff .
     pylint: {envpython} -m pylint --version
     pylint: {envpython} -m pylint AttributeWrapper tests
-    format: {envpython} -m autopep8 -v -aa --in-place --recursive Attribute_wrapper/
+    format: {envpython} -m autopep8 -v -aa --in-place --recursive attribute_wrapper/
     format: {envpython} -m autopep8 -v -aa --in-place --recursive tests/
     format: {envpython} -m black -v .