Added NSManagedObjectContext+ChainSave method just like the [MagicalRecord saveWithBlock…] methods, this set of methods start with the receiver context and creates a child context. Upon saving, the child context saves to parent and chain up the save operation to main context, and finally to saving context. This is to ensure that all changes made in background will pass through to main context and then to persistent store.
Remove commented line

Removing sloppy commented line!
fix link typo
fix the link, this time for real
Added unit test
Updated method names
Updated unit test
Merge remote-tracking branch 'ma/develop' into develop

Conflicts:
	MagicalRecord.xcodeproj/xcshareddata/xcschemes/libMagicalRecord-OSX.xcscheme
	MagicalRecord.xcodeproj/xcshareddata/xcschemes/libMagicalRecord-iOS.xcscheme
Merge pull request #916 from DivineDominion/patch-1

Fix typo in link to Apple's documentation
Merge pull request #901 from hungtruong/develop

Remove unnecessary comment-out line of code
Merge pull request #843 from callzhang/develop

Added methods to support chained saves on NSManagedObjectContext
Sort test target source
Remove unused methods
Move calls to `MR_setWorkingName:` inside the `performBlockAndWait:` block to fix potential thread access issues
Update documentation to use headerdoc.
Formatting and casting fixes
Remove redundant or non-required header imports
Update category name, and header comments
Fix copyright year