Bump version key to 0.8.4

Fix branch name

Add IMPALA xlarge config file

Revert "Use Boost.Process instead of pid_t (ray-project#6510)" (ray-p…

…roject#6909)

This reverts commit fb8e361.

require packaging (ray-project#6517)

Make sure numpy >= 1.16.0 is installed for fast pickling support (ray…

…-project#6486)

* Make sure numpy >= 1.16.0 is installed

* Works for 1.15.4

* lint

* formatting

* update

* put check into the right place

* lint

Fix str of RayTaskError (ray-project#5878)

* fix key error

* fix

[rllib] Properly flatten 2-d observations as input to FCnet (ray-proj…

…ect#5733)

bump version to 0.7.5

[rllib] Revert [rllib] Port DDPG to the build_tf_policy pattern (ray-…

…project#5626)