RestKit/RestKit — pull request #1570 by almassapargali (2013-08-25 08:10:29+00:00)
Title: changed Error code when response mapping declined with `willMapDeserializedResponseBlock` block

According to documentation [here](http://restkit.org/api/latest/Classes/RKResponseMapperOperation.html#//api/name/setWillMapDeserializedResponseBlock:) when block returns nil mapping operation should fail with an error with the RKMappingErrorMappingDeclined code.