Added new pre-flight delegate callbacks for customization of RKRequest and RKObjectLoader instances before dispatch

Code/ObjectMapping/RKObjectLoader.h

@@ -80,6 +80,16 @@ typedef void(^RKObjectLoaderDidLoadObjectsDictionaryBlock)(NSDictionary *diction
  */
 - (void)objectLoaderDidFinishLoading:(RKObjectLoader *)objectLoader;
 
+/**
+ Informs the delegate that the object loader has serialized the source object into a serializable representation
+ for sending to the remote system. The serialization can be modified to allow customization of the request payload independent of mapping.
+ 
+ @param objectLoader The object loader performing the serialization.
+ @param sourceObject The object that was serialized.
+ @param serialization The serialization of sourceObject to be sent to the remote backend for processing.
+ */
+- (void)objectLoader:(RKObjectLoader *)objectLoader didSerializeSourceObject:(id)sourceObject toSerialization:(inout id<RKRequestSerializable> *)serialization;
+
 /**
  Sent when an object loader encounters a response status code or MIME Type that RestKit does not know how to handle.
  

Code/ObjectMapping/RKObjectLoader.m

@@ -351,6 +351,10 @@
             [self didFailLoadWithError:error];
             return NO;
         }
+        
+        if ([self.delegate respondsToSelector:@selector(objectLoader:didSerializeSourceObject:toSerialization:)]) {
+            [self.delegate objectLoader:self didSerializeSourceObject:self.sourceObject toSerialization:&params];
+        }
 
         self.params = params;
     }

Code/ObjectMapping/RKObjectSerializer.m

@@ -90,7 +90,7 @@
     return nil;
 }
 
-- (id<RKRequestSerializable>)serializationForMIMEType:(NSString*)MIMEType error:(NSError**)error {    
+- (id<RKRequestSerializable>)serializationForMIMEType:(NSString *)MIMEType error:(NSError **)error {
     if ([MIMEType isEqualToString:RKMIMETypeFormURLEncoded]) {
         // Dictionaries are natively RKRequestSerializable as Form Encoded
         return [self serializedObject:error];