* Reimplemented connection tests to work with `RKConnectionDescription`. Introduced new `RKConnectionTestExpectation` class
* Slimmed down API by removing proxy methods on `RKMappingTest`
* Eliminated `verifiesOnExpect` behavior in favor of using `evaluateExpectation:`
* Ensured compatibility with RKKiwiMatchers
* Replaces primary key with `RKEntityIdentifier`
* Add support for use of compound keys for object identification
* Refactor `RKConnectionMapping` to `RKConnectionDescription` and add support for connecting with multiple attributes
* Clarify naming of representation key methods to better match naming conventions
* Add type transformation support for object identification
* Greatly expand test coverage for object identification
* Drop the `NSEntityDescription` category
* Simplify the `RKManagedObjectCaching` protocol
* Add compound key support to the Fetch Request and In Memory Cache implementations
* Replace Kiwi with Specta for tests where contexts are helpful for organization
* Rename `defaultValueForMissingAttribute` to `defaultValueForAttribute`
* Enable evaluation blocks to return an NSError describing the failure
* Align all RKAttributeMapping references to RKPropertyMapping
* Cleanup docs
* Add `RKMappingTestExpectationTestCondition` macro for succinctly implementing mapping test evaluation blocks
* Clean up descriptions for better output from Kiwi
* Added error domain and codes specific for the mapper
* Migrated from using an NSString to real NSError objects
* Toned down the verbosity of error output for readability
* Cleaned up comment formatting
* Changed RKAttributeMapping to RKPropertyMapping for better alignment with the realities of the data model
set due to an unchanged value. Update RKMapperTest to correctly validate mappings that do not result
in a value change (typically nil => nil). closes#72, fixes#634
the property to support testing portions of the mapping not expressed via key path transformations
(the connection of Core Data relationships, for example).
