Documentation fix

I found that following the docs as-is didn't let me run the tests. I tested this doc fix by running the commands and verifying that no step failed.

The only question I have is whether you want to include the `python setup.py develop` step as-is. Running the tests won't work without that or `python setup.py install` and I opted for `develop` because the documentation is in the testing section. But it's up to you.