Adding a note about third party JSON libraries to the requirements se…

…ction.

README.md

@@ -113,6 +113,12 @@ NSOperationQueue *queue = [[[NSOperationQueue alloc] init] autorelease];
 
 AFNetworking requires either [iOS 4.0](http://developer.apple.com/library/ios/#releasenotes/General/WhatsNewIniPhoneOS/Articles/iPhoneOS4.html%23//apple_ref/doc/uid/TP40009559-SW1) and above, or [Mac OS 10.6](http://developer.apple.com/library/mac/#releasenotes/MacOSX/WhatsNewInOSX/Articles/MacOSX10_6.html#//apple_ref/doc/uid/TP40008898-SW7) and above.
 
+AFNetworking uses [`NSJSONSerialization`](http://developer.apple.com/library/mac/#documentation/Foundation/Reference/NSJSONSerialization_Class/Reference/Reference.html) if it is available. If your app targets a platform where this class is not available you can include one of the following JSON libraries to your project for AFNetworking to automaticly detect and use.
+
+* [JSONKit](https://github.com/johnezang/JSONKit)
+* [SBJson](http://stig.github.com/json-framework/)
+* [YAJL](http://lloyd.github.com/yajl/)
+
 ### ARC Support
 
 If you are including AFNetworking in a project that uses [Automatic Reference Counting (ARC)](http://clang.llvm.org/docs/AutomaticReferenceCounting.html) enabled, you will need to set the `-fno-objc-arc` compiler flag on all of the AFNetworking source files. To do this in Xcode, go to your active target and select the "Build Phases" tab. In the "Compiler Flags" column, set `-fno-objc-arc` for each of the AFNetworking source files.