- Fix meta-parameter usage on tutorials.
- Install tutorial dependencies on CI.
- Switch from `requirements-test.txt` to `extras_require` for test dependencies, and also use it for tutorial dependencies.
- Make some performance tests deterministic.
Run:
```
isort ./python
autopep8 -i --ignore E501,E701,E731 $(find ./python/ -name '*.py')
```
with an `.isort.cfg` and then clean up a few warts. This PR should be a no-op; the idea is that this is all boring whitespace changes, and any config file changes will be in a different change to make it easier to review.