Merge pull request AFNetworking#35 from evanlong/master

Consistent use of main thread for success/failure callbacks in AFJSONRequestOperation

Author: Mattt Thompson

AFNetworking/AFJSONRequestOperation.m

@@ -84,11 +84,15 @@ + (id)operationWithRequest:(NSURLRequest *)urlRequest
 
         if (error) {
             if (failure) {
-                failure(request, response, error);
+                dispatch_async(dispatch_get_main_queue(), ^{
+                    failure(request, response, error);
+                });
             }
         } else if ([data length] == 0) {
             if (success) {
-                success(request, response, nil);
+                dispatch_async(dispatch_get_main_queue(), ^{
+                    success(request, response, nil);
+                });
             }
         } else {
             dispatch_async(json_request_operation_processing_queue(), ^(void) {