Eliminate strong/weak child contexts.

Conflicts:

	AFIncrementalStore/AFIncrementalStore.m
Missed an instance where context saves weren't taking place correctly.

Conflicts:

	AFIncrementalStore/AFIncrementalStore.m
Refactoring managed object context save with exceptional behavior
Locking the persistent store coordinator is not necessary with private queue contexts.
Send fetched objectIDs instead of objects in notification
Use CFAbsoluteTimeGetCurrent() as newValues incremental store node
Fixing deadlock by wrapping AFHTTPRequestOperation success callbacks in context performBlock
Remove unnecessary completion dispatch queue setting for batched requests
Adding missing performBlockAndWait calls
Fixing flash of empty toMany relationship issue, caused by empty array being returned in -newValueForRelationship:...