1. My script:
	- Extract the specified answers from ZhiHu specified page
	- Generate new html for this answer
	- html --> mobi

TODO:

Refine the format:
	- force the image play on single page
	- Add the question title and  author info

1. html --> mobi now was completed by calibre manully. May be it's better
   do it use python to execute some cmd.
2. User interface:
	- specified the input url
		- choose one answer from this page
	- specified the output path
		- automatically package to .zip
		- create new dir for the output, because it may contains:
			- new_doc.html
			- several *.jpg files
	- send mail to specified kindle mail-box
3. Wrap this program to a chrome/firefox extension, this may need:
	- Use the SAE as server
	- Learn the extension development