Merge pull request #134 from u0u0/master

add wiki articles
Update zh.md
remove useless bada pages, refactor catalog for zh
Merge pull request #135 from walzer/master

remove useless bada pages, refactor catalog for zh
Update zh.md
Update zh.md
update demo for chapter 1.
issue #3966, Tower defense game chapter2.
issue #3966, Tower defense game chapter3.
fixed #3966, Tower defense game chapter3.