Convert Microsoft Word HTML to GitHub Flavored Markdown

1. Save a Word documents as HTML
2. Convert encoding from gb2312 to utf8. And fix the charset value in HTML metadata.
3. Convert the clean html with pandoc

   iconv -f gb2312 -t utf-8 input.html | sed -e "s/charset=gb2312/charset=utf8/g" | pandoc -f html -t markdown_github -o output.md