YAPF, take 3 (#2098)

* 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

python/ray/monitor.py

@@ -503,11 +503,13 @@ class Monitor(object):
             self.cleanup_task_table()
         if len(self.dead_plasma_managers) > 0:
             self.cleanup_object_table()
+
+        num_plasma_managers = len(self.live_plasma_managers) + len(
+            self.dead_plasma_managers)
+
         log.debug("{} dead local schedulers, {} plasma managers total, {} "
                   "dead plasma managers".format(
-                      len(self.dead_local_schedulers),
-                      (len(self.live_plasma_managers) + len(
-                          self.dead_plasma_managers)),
+                      len(self.dead_local_schedulers), num_plasma_managers,
                       len(self.dead_plasma_managers)))
 
         # Handle messages from the subscription channels.