Some introductory changes

I've tried to clarify a point that is very confusing to new users. PLEASE CHECK THE INFO I'VE ADDED, there are certain points that I'm not entirely sure of. (Like cocos2d-iphone becoming cocos2d-swift, I've just found out about that one)
Roger that..

But I do think you guys need to add this info somewhere, a lot of people has trouble grasping this.