v 2.2.2 by minyangyang.
更新nerdcommenter文档
Update README.md, add 'NERD_commenter'

更新 README.md，增加插件 NERD_commenter 的中文文档

该文档取自
https://github.com/codepiano/NERD_commenter.cnx/blob/master/doc/NERD_commenter.cnx
该版本的提交为
https://github.com/codepiano/NERD_commenter.cnx/commit/a14bfbcc5fcd86ee947f43393c039f5306384312
对应的 NERD_commenter 插件为
https://github.com/scrooloose/nerdcommenter/blob/master/plugin/NERD_commenter.vim
对应的英文文档为
https://github.com/scrooloose/nerdcommenter/blob/master/doc/NERD_commenter.txt
Merge pull request #6 from Firef0x/nerdcommenter

Feature Request: Add doc for plugin 'NERD_commenter'