translate getting-started/your-first-multi-screen-site/content.html, except samples
Merge pull request #1 from lostlandark/master

merge upstream
Merge pull request #2 from lostlandark/master

merge upstream
little fix
Merge branch 'master' of https://github.com/yestinchan/google-web-fundamentals-simplified-chinese.git
Merge pull request #9 from yestinchan/master

Translate content of your-first-multi-screen-site