* add PPO example

* Update Readme

* Update Readme

* fix codestyle

* Update Readme

* refine action mapping

* add more unitest case

* remove unnecessary params initialize, add more comments, add benchmark result

* rename

* remove PARL dependence in readme of examples

* add logger module

* refine comment

* add license

* refine set_level api

* refine unittest

* fix codestyle with yapf

* add termcolor dependency