Updating notes about ARC and requirements

README.md

@@ -143,7 +143,17 @@ operation.outputStream = [NSOutputStream outputStreamToMemory];
 
 ## Requirements
 
-AFNetworking requires either [iOS 5.0](http://developer.apple.com/library/ios/#releasenotes/General/WhatsNewIniPhoneOS/Articles/iPhoneOS4.html) and above, or [Mac OS 10.7](http://developer.apple.com/library/mac/#releasenotes/MacOSX/WhatsNewInOSX/Articles/MacOSX10_6.html#//apple_ref/doc/uid/TP40008898-SW7) ([64-bit with modern Cocoa runtime](https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtVersionsPlatforms.html)) and above.
+AFNetworking 1.0 and higher requires either [iOS 5.0](http://developer.apple.com/library/ios/#releasenotes/General/WhatsNewIniPhoneOS/Articles/iPhoneOS4.html) and above, or [Mac OS 10.7](http://developer.apple.com/library/mac/#releasenotes/MacOSX/WhatsNewInOSX/Articles/MacOSX10_6.html#//apple_ref/doc/uid/TP40008898-SW7) ([64-bit with modern Cocoa runtime](https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtVersionsPlatforms.html)) and above.
+
+For compatibility with iOS 4.3, use the latest 0.10.x release.
+
+### ARC
+
+AFNetworking uses ARC as of its 1.0 release.
+
+If you are using AFNetworking 1.0 in your non-arc project, you will need to set a `-fobjc-arc` compiler flag on all of the AFNetworking source files. Conversely, if you are adding a pre-1.0 version of AFNetworking, you will need to set a `-fno-objc-arc` compiler flag.
+
+To set a compiler flag in Xcode, go to your active target and select the "Build Phases" tab. Now select all AFNetworking source files, press Enter, insert `-fobjc-arc` or `-fno-objc-arc` and then "Done" to enable or disable ARC for AFNetworking.
 
 ## Credits