Gitbook是一个命令行工具，使用方法：
**本地预览**
~~~
$ gitbook serve ./图书名称
~~~
**输出一个静态网站**
~~~
$ gitbook build ./repository --output=./outputFolder
~~~
**查看帮助**
~~~
$ gitbook -h
Usage: gitbook [options] [command]
Commands:
build [options] [source_dir] Build a gitbook from a directory
serve [options] [source_dir] Build then serve a gitbook from a directory
pdf [options] [source_dir] Build a gitbook as a PDF
ebook [options] [source_dir] Build a gitbook as a eBook
init [source_dir] Create files and folders based on contents of SUMMARY.md
Options:
-h, --help output usage information
-V, --version output the version number
~~~
