Merge pull request #26 from christianklotz/master

Fix #22 and allow `null` values in JSON when interoperating with Swift

Author: Josh Holtz

Classes/JSONAPIErrorResource.h

@@ -6,6 +6,8 @@
 //  Copyright (c) 2015 Josh Holtz. All rights reserved.
 //
 
+#import <Foundation/Foundation.h>
+
 /**
  *  Class respresentation of a JSON-API error structure.
  */

Classes/JSONAPIResourceParser.m

@@ -205,7 +205,7 @@ + (void)set:(NSObject <JSONAPIResource> *)resource withDictionary:dictionary {
 
         } else {
             id value = [attributes objectForKey:[property jsonName]];;
-            if (nil == value) {
+            if ((id)[NSNull null] == value) {
                 value = [dictionary objectForKey:[property jsonName]];
             }