Set Xcode compatibility to Xcode 6.3 and up.

AFNetworking.xcodeproj/project.pbxproj

@@ -3,7 +3,7 @@
 	archiveVersion = 1;
 	classes = {
 	};
-	objectVersion = 46;
+	objectVersion = 47;
 	objects = {
 
 /* Begin PBXBuildFile section */
@@ -805,7 +805,7 @@
 				};
 			};
 			buildConfigurationList = 299522331BBF104D00859F49 /* Build configuration list for PBXProject "AFNetworking" */;
-			compatibilityVersion = "Xcode 3.2";
+			compatibilityVersion = "Xcode 6.3";
 			developmentRegion = English;
 			hasScannedForEncodings = 0;
 			knownRegions = (