Option to print help to std out

Thanks for creating Fire. It's a fantastic argument parsing tool.

A minor request: I prefer my help strings to be printed to stdout instead of a console like `less`. When the output is sent to a `less`-like program you can't reference the script argument information when trying to type your next command.

The naive way to allow this option is adding a switch so the user can choose to send information console package or to stdout (code below).

https://github.com/google/python-fire/blob/d77453938a4b7a5a2bb71d9cb40397ee8bbc2e0a/fire/core.py#L171
to something like
```
if print_std:
print(text, file=out)
else:
console_io.More(
```

I don't see an elegant way to set `print_std` in your source code since you are not accepting contributions to your console package and the `Display` function is not a method of the Fire class. I don't see a straightforward way to have the user set this display option. Obviously, you know the code better than me so you may know a good way to add this option.

I am using fire version 0.2.1 and have seen this behavior with Ubuntu 16.04 and 18.04.

Thank you for your time!

首先閱讀第 171 行附近的 fire/core.py，以及關於 console_io.More 和 stdout 處理的 issue 討論。確定應如何提供使用者可選擇的顯示選項，然後驗證 help 可以傳送到 stdout，而不會出現目前類似 pager 的行為，同時保留現有的預設設定。

由索引模型根據 Issue 內容生成。