Revert "Add shell script for downloading cocos2d 3.0 library"

This reverts commit 8808fd41fc025d158f08937bf8061a291043be86.
Add cocos2d-x 3.0
[migrating] fix physics collision
[migrating] Fix bird death animation

- Fixed rotation direction.
- Fixed fade out animation.

Object opacity and fading animation of cocos2d-x was broken in v3.0b2.
The bird disappearing issue emerged when fading is partially fixed in
v3.0.  However, keep in mind that there are still opacity stuff broken.