IteratingSystem uses entities.values() rather than entities.entries() as it's faster
Entity uses a Bag of Component objects indexed by their ComponentType index for super fast access
ComponentMapper is used to efficiently retrieve components from an Entity
Makes some methods in Entity package protected, reducing complexity in the API
Makes componentAdded and componentRemoved final in Entity
Updates tests with the new API
Nothing outside core uses ComponentType, so I made it package protected
and final
Simplified loops in Engine
Merge pull request #38 from siondream/performance

Performance improvements