* Metadata mapping is implemented via an `NSProxy` object that stands in for the `sourceObject` of each `RKMappingOperation`
* Key paths that are prefixed with `@metadata.` are mapped against the `metadata` dictionary of the operation, else they hit the `sourceObject`.
* Metadata is implemented by merging a dictionary of data in from `RKObjectRequestOperation`, through to `RKResponseMapperOperation`, into `RKMapperOperation`, and all the way down into the `RKMappingOperation`, where it is available to each object. By convention, metdata is namespaced into subdictionaries.
* 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
* 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
* Reworked execution of relationship connection operations to use dependencies instead of queue suspension.
* Migrates responsibility for connecting relationships from `RKManagedObjectRequestOperation` into `RKManagedObjectResponseMapperOperation`. This ensures that you get a mapped and connected object graph back from the response mapper if you are using it outside of a request operation.
* Add `parentOperation` to managed object mapping data source to establish dependencies.
