EDQueue, update enum definition
EDQueue, remove UIKit type (Foundation only class)
EDQueue, move delegate definition to bottom
EDQueue, add a completion block type for convenience
EDQueue, remove macro
EDQueue, explicitly declare properties as non-atomic, use BOOL type
EDQueue, object's calloc'd
EDQueue, explicitly declare ivars, use BOOL type
EDQueue, move dealloc to init
EDQueueStorageEngine, hide types internally
EDQueueStorageEngine, move dealloc under init
EDQueueStorageEngine, use BOOL type, rename private methods with _*