* Change contract to the use the `description` method instead of `errorMessage`. This makes it work with any class out of the box
* Add import for RKErrorMessage to the Support.h header so it is immediately available
* Fix incorrect keyPath in the README.md
* Add additional notes about how the errors are constructed to the README
* Inversing non intelligently walks the mapping graph, ensuring that cyclic graphs are resolved properly
* Copy all attributes from the parent to the inverse mapping (date formatters, etc)
* 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`
* Renamed RKObjectPaginator to RKPaginator for simplicity
* Removed delegate on paginator in favor of simple success/failure blocks
* Added `willMapDeserializedResponseBlock` for manipulating the response body before mapping begins
* Added support for cancelling an in-progress pagination request
* Passes through cancellation from object request operation to HTTP request operation and response mapping operation. closes#993
* Performs all object mapping within an NSOperationQueue to enable constraining of mapping activities.
* Add default mapping queue with concurrency limit of 1 operation.
* Migrate deserialization of the response body into a serial dispatch queue to ensure that only one parse occurs at a time.
* RKObjectParameterization now returns an empty dictionary if mapping produces an unmappable representation error (no mappable attributes/relationships found)
* Log errors if request construction results in an NSError and return nil
* Ensure errors are passed back up through object parameterization instead of just returning nil
* Reset the serialization MIME Type registry during RKTestFactory set up to ensure it is in a sane state
* Convert Hamcrest matchers to Expecta in the object mapper tests to fix infinite recursion on test failure (will need to completely phase out Hamcrest soon)
