* Use pep8 style
The original style file is actually just pep8 style, but with everything
spelled out. It's easier to use the `based_on_style` feature. Any overrides are
clearer that way.
* Improve yapf script
1. Do formatting in parallel
2. Lint RLlib
3. Use .style.yapf file
* Pull out expressions into variables
* Don't format rllib
* Don't allow splits in dicts
* Apply yapf
* Disallow single line if-statements
* Use arithmetic comparison
* Simplify checking for changed files
* Pull out expr into var