GUI系の概要
Merge pull request #611 from haruni2014/master

Added "Overview of GUI system"
CocoStudioの表記をCocos Studioに修正
Merge pull request #612 from haruni2014/master

"CocoStudio" changes "Cocos Studio"
Cocos::Valueについて英文を日本語訳
Merge pull request #613 from ulzexus/master

Cocos::Valueについて英文を日本語訳