Outlined methods in headers.

Outlined the methods necessary to add support for custom store URLs.
Added Support For Custom Working Directories (1/3)

Added support to iCloud stores.
Added Support For Custom Working Directories (2/3)

Added support to standard setup.
Added Support For Custom Working Directories (3/3)

Added support to NSPersistentStoreCoordinator category.
Added test for custom working directories.
Fixed incompatible pointer types error.
Fixed URL error.
Fixed error with creating a NSURL from a path.
Added back public method in MagicalDataImport

Fixes #821
Merge pull request #833 from ryanjm/add-importValuesForKeysWithObject

Make `-MR_importValuesForKeysWithObject:` a public method again
Combined two functionally identical methods
Replace NSPersistentStoreCoordinator's `lock` and `unlock` methods as they are deprecated in iOS 8.0 and OS X 10.10
Restore lock/unlock under iOS 7.x and OS X 10.9
Revert! Revert! This can be fixed in MagicalRecord 3.0
Once more, with feeling…
Use non-deprecated methods when targeting iOS 8.0
Merge branch 'develop' into pr/822

Conflicts:
	MagicalRecord/Categories/NSPersistentStoreCoordinator+MagicalRecord.m
Merge pull request #853 from magicalpanda/pr/822

Add support for custom working directories
Fix a few concurrency issues for iOS 8
Revert root context thread handling

Fixes #565