- Added a time variable and a time label that counts the number of
seconds that the user has been playing for
 - Refactored setting the orbitIndex from the Entity initializer to the
Player's initializer
Merge branch 'feature-time_counter' into development
Enemy spawning is implemented

 - Added enemy sprites
 - Created the Enemy class
 - Refactored code that should be in Entity from Player
 - Reversed Z order
 - An Enemy spawns every 5 seconds
 - Enemies spawn at orb and fly out
Merge branch 'feature-enemies_spawning' into feature-enemies
Enemies can despawn

 - Added a life counter to Enemy
 - Added a despawn flag to Enemy
 - Enemies can fly off screen after their life has passed a number
Stopping iOS 6 development
Merge branch 'feature-enemies_despawn' into feature-enemies
Merge branch 'feature-enemies' into development