Fix README typo

Cocoa vs Cocos, fight!
Fix naming convention.

1. cocos_2d & box2d to cocos2d & box2d
2. bbp* macros to jbp* macros
Fix typo
Fix naming convention for sample app
Merge pull request #4 from kastiglione/patch-1

Fix: Read Me
Merge pull request #5 from yonekawa/feature/naming_convention

Adds: Improve naming convention
Adds:
  => ReadMe: The Box2D wrapper URL