Beginnings of a TwitterManager class

The TwitterManager will abstract out all of the Twitter API
communication on behalf of GameState etc.
Trends are now being fetched.
Merge master branch into twintegration.
Starts refactoring for more complicated structure.

We'll need other singletons later (eg Twitter), so I'm grouping those.
The Sprite classes are also about to become more than plain sprites,
and to inherit from a common parent, thus the Objects group.
Add a constant for detecting whether we are in debug mode.
Common protocols file added.

This is used to keep loose coupling between classes.
Merging master branch into twintegration branch
Adds shared parent class for Hero and Projectile.
Removing a few imports that are no longer needed.
Refactor the GameState singleton to use iOS's dispatch_once.
Placeholder code for the Hero's state machine and interactions.
Cherry pick change 7d8ab1a30a into twintegration branch.
Rewrite the TwitterManager class to resolve issues talking to the Twitter API.
Move the TwitterManager classs to it's own directory.
Change how we do Twitter.

We can now get trending hashtags and find tweets for them. #incredible
Adds GameManager class.

The GameManager is used to decouple scenes from eachother.
Moved scene shortcuts in with the other enums.
Moved the Hero's Box2D setup inside the hero.

The GameLayer (and wider world) shouldn't care about the Hero's physics
setup. Also reduces cruft in the GameLayer.
Moves projectile physics setup code into Projectile class.
Create and use a Tweet object.