issue #3503. modify event dispatcher article
Merge pull request #71 from andyque/master

issue #3503. modify event dispatcher article
fixed #3298, modify spell, coding style, wrong grammar. update wrong screenshot.
Merge branch 'master' of https://github.com/cocos2d/cocos-docs
Merge pull request #72 from Ivenyang/master

fixed #3298, modify spell, coding style, wrong grammar. update wrong screenshot.
issue #3298, change header description.
issue #3298, change header description.
Merge pull request #73 from u0u0/master

issue #3298, change header description.