* add save_param in docs and quickstart

* Update train.py

* remove previous algorithms; use the forward function in parl.Model

* remove abundant lines

* yapf

* intra-version: move parl.framework into parl.core.fluid

* add folder: parl.core

* remove former test folders

* yapf

* yapf0.24

* make the quickstart more compact

* remove args in the main function

* yapf

* add gif

* remove render

* Update README.md

* Update README.md

* Update README.md

* add DDPG example, fix some tiny bug

* add license

* unify code structure

* unify code structure

* refine gputils, fix seed in QuickStart

* use white noise in DDPG

* fix codestyle

* add a episode to show the final test reward

* make code more clear

* add QuickStart example, refine DQN example

* add examples link

* refine the naming, and add quick start training result