Add stdout and stderror capturing with python behave

#### I'm submitting a ...
- [ ] bug report
- [x] feature request

#### What is the current behavior?
Output from stdout and stderror is not captured for the report when using allure-behave.

#### What is the expected behavior?
Stdout and stderror output should be available when viewing Overview for the test.

#### What is the motivation / use case for changing the behavior?
To have an easy way to see the test-related output for future debugging/bug reporting/etc.

#### Please tell us about your environment:
- Allure version: 2.4.1
- Test framework: behave@1.2.6
- Allure adaptor: allure-behave@2.6.5

首先跟踪 allure-behave 与 behave@1.2.6 的集成，以及当前如何将测试输出传递到报告中。使用所述的 Allure 和 allure-behave 版本作为复现环境，验证测试的 Overview 是否同时暴露 stdout 和 stderr。

由索引模型根据 Issue 内容生成。