translated pwd V1.0 by Vic020
Merge pull request #6 from Vic020/master

translated pwd V1.0 by Vic020，也请提交译文，只有生成了译文才表示格式上正确，而且也应该通读过译文了。
Merge github.com:LCTT/man-pages
complete the translation of man1/sleep.1 by will.qian