added command line options and explanation about how the article name is derived

Author: abeggchr

README.md

@@ -56,7 +56,33 @@ or, For example:
 $ book sm -r ../sailsjs-docs-gitbook/en -i 0home -u 'myApp' -c 'concepts, reference, userguides' -n "Sails.js 官方文档(中英合辑）"
 ```
 
-**Note**： `-s` or `--sortedBy` can not be given `-`, commander.js will parse it an option. But you can set it in `book.json` as follow.
+To see the command line options:
+
+```
+$ book sm --help
+
+ Usage: summary|sm [options]
+
+ Generate a `SUMMARY.md` from a folder
+
+ Options:
+
+ -h, --help output usage information
+ -r, --root [string] root folder, default is `.`
+ -n, --bookname [string] book name, default is `Your Book Name`.
+ -c, --catalog [list] catalog folders included book files, default is `all`.
+ -i, --ignores [list] ignore folders that be excluded, default is `[]`.
+ -u, --unchanged [list] unchanged catalog like `request.js`, default is `[]`.
+ -o, --outputfile [string] output file, defaut is `./SUMMARY.md`
+ -s, --sortedBy [string] sorted by sortedBy, for example: `num-`, defaut is sorted by characters
+ -d, --disableTitleFormatting don't convert filename/folder name to start case (for example: `JavaScript` to `Java Script`), default is `false`
+
+```
+
+**Notes**： 
+* The article title is taken from `title` property in the articles front-matter. If this property is not available, the articles filename will be used as title for the summary. 
+* The option `-s` or `--sortedBy` can not be given `-` as argument, because commander.js will parse it an option. But you can set it in `book.json` as follows.
+
 
 2> Create a `book.json` in the book`s root folder