improve facebook documentation
Update en.md
Update en.md
Update en.md
Merge pull request #571 from tczbzb/patch-13

Update en.md
Update en.md
Merge pull request #570 from tczbzb/patch-12

Update en.md
Merge pull request #572 from tczbzb/patch-14

Update en.md
Merge pull request #565 from joshuastray/master

improve facebook documentation
Merge pull request #569 from pandamicro/master

[Cocos2d-JS PG] Add english doc for director of game
[Cocos2d-JS PG] Add chinese doc for director of game
[Cocos2d-JS PG] Improve english doc for director of game
Merge branch 'master' of https://github.com/cocos2d/cocos-docs