Merge pull request #554 from pandamicro/master

[Cocos2d-JS] Improve programming guide and Facebook docs
add v2 manual
Merge pull request #555 from hdecember/master

add v2 manual
update doc
Merge pull request #556 from hdecember/master

update doc
[Cocos2d-JS] Docs for v3.1 release
Merge branch 'master' of https://github.com/cocos2d/cocos-docs