Merge pull request #1 from google/master

Added support for translating the _betterbook.yaml file
Create localized_string/zh-cn.json
Merge branch 'master' of https://github.com/viztor/WebFundamentals
add optimize-images-for-performance.markdown to _zh-cn
translate optimize-images-for-performance.markdown
Merge pull request #934 from viztor/master

Create localized_string/zh-cn.json
Merge pull request #944 from chenxsan/optimize-images

Translated optimize-images-for-performance.markdown
Localized strings for primary languages
Translates the try it now button
Do not translate Web Starter Kit
Fixes #946 - adds zh-cn docs
Fixes #948 - adds German
Adds German to the mix
IW/HE file name correction
Fixes #950 - adds French