About keeping `elegantrl_helloworld` simple.

[Yonv1943]

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我们想让 elegantrl_helloworld 容易安装、运行、阅读。 We want to keep elegantrl_helloworld easy to install/ run/ read.

• 容易安装：只需安装 torch 和 gym

• 容易运行：只有四个核心文件 agent.py, net.py, run.py, config.py

• 容易阅读：总代码行数不超过1000行

• easy to install: only need to install torch and gym

• easy to run: only 4 kernel files: agent.py, net.py, run.py, config.py

• easy to read: the total code number less than 100 lines.

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举个例子：yaml 更适合放在 完整版的elegantrl里，但不适合放在 elegantrl_hellowworld里 For example: yaml fits better in the full version of elegantrl, but not in elegantrl_hellowworld.