Adding include paths to CLI testrunner

I think it would be useful to have something like --include=PATH for the CLI testrunner. That way you can setup your testsuite without having to know about the actual location of the test suite in the directory structure. The call to the CLI testrunner then can take care of setting up the enviroment using --include. No need to repeat

```
require =("../lib/LibrarySubjectToBeTested");
```

but do

```
require('LibrarySubjectToBeTested");
```

and simply call

```
nodeunit --include=../lib/
```

I implemented a patch that would add this functionality to the testrunner. Have a look at it: 1db0b284d70829d4fe5f8a1fe20274562cdc5bd8
Please let me know what you think and if there's anything I missed. If you like it, feel free to pull it in.

首先检查 commit 1db0b284d70829d4fe5f8a1fe20274562cdc5bd8 和 CLI testrunner 入口点。检查提议的 --include=PATH 选项如何设置模块查找环境，然后运行现有测试套件；当 nodeunit --include=../lib/ 可以在不使用相对路径的情况下 require LibrarySubjectToBeTested 时，即表示完成。

由索引模型根据 Issue 内容生成。