Append parent dir to sys.path for autodoc
Append parent dir to sys.path for autodoc

This was previously failing with:

index.rst:158: WARNING: autodoc can't import/find class
'flaskext.testing.TestCase', it reported error: "No module named
flaskext.testing", please check your spelling and sys.path

Now the rendered docs include the API docs.

ecarrara/flask-testing,jmagnusson/flask-testing,ecarrara/flask-testing,jmagnusson/flask-testing