Updating CocoaPods install instructions

Author: lostintangent

README.md

@@ -120,10 +120,10 @@ We hope to eventually remove the need for steps #2-4, but in the meantime, RNPM
     pod 'CodePush', :path => './node_modules/react-native-code-push'
     ```
 
-    CodePush depends on an internal copy of the `SSZipArchive` library, so if your project already includes that (either directly or via a transitive dependency), then you can install a version of CodePush which excludes it by using the following subspec:
+    CodePush depends on an internal copy of the `SSZipArchive` library, so if your project already includes it (either directly or via a transitive dependency), then you can install a version of CodePush which excludes it by depending specificaly on the `Core` subspec:
 
     ```ruby
-    pod 'CodePush', :path => './node_modules/react-native-code-push', :subspecs => ['NoZip']
+    pod 'CodePush', :path => './node_modules/react-native-code-push', :subspecs => ['Core']
     ```
 
     *NOTE: The above paths needs to be relative to your app's `Podfile`, so adjust it as nec