Only require CFNetwork on iOS so that podspec works on Lion

SocketRocket.podspec

@@ -8,6 +8,7 @@ Pod::Spec.new do |s|
   s.source_files = 'SocketRocket/*.{h,m,c}'
   s.clean_paths  = %w{SRWebSocketTests SocketRocket.xcodeproj TestChat TestChatServer TestSupport extern}
   s.requires_arc = true
-  s.frameworks   = %w{CFNetwork Security}
+  s.frameworks   = %w{Security}
+  s.frameworks << 'CFNetwork' if config.ios?
   s.libraries    = "icucore"
 end