prepare for 4.0.0

Author: davidtruong

IterableSDK.podspec

@@ -16,7 +16,7 @@ Pod::Spec.new do |s|
   #
 
   s.name         = "IterableSDK"
-  s.version      = "3.1.1"
+  s.version      = "4.0.0"
   s.summary      = "Iterable's official SDK for iOS"
 
   s.description  = <<-DESC

README.md

@@ -1,6 +1,6 @@
 [![CocoaPods](https://img.shields.io/cocoapods/v/IterableSDK.svg?style=flat)](https://cocoapods.org/pods/IterableSDK)
 [![License](https://img.shields.io/cocoapods/l/IterableSDK.svg?style=flat)](https://opensource.org/licenses/MIT)
-[![Docs](https://img.shields.io/cocoapods/metrics/doc-percent/IterableSDK.svg?style=flat)](http://cocoadocs.org/docsets/IterableSDK/3.1.1/)
+[![Docs](https://img.shields.io/cocoapods/metrics/doc-percent/IterableSDK.svg?style=flat)](http://cocoadocs.org/docsets/IterableSDK/4.0.0/)
 
 # Iterable iOS SDK
 
@@ -67,7 +67,8 @@ In the `Artifacts` directory, you can find the compiled static library and heade
 
 # Using the SDK
 
-1. Once you know the email of the user, **create a shared instance of an `IterableAPI`**
+1. Once you know the email or userId of the user, **create a shared instance of an `IterableAPI`**
+  * If you are initializing using a userId, an existing user must already exist for that userId
   * use `[IterableAPI sharedInstanceWithApiKey:(NSString *)apiKey andEmail:(NSString *)email launchOptions:(NSDictionary *)launchOptions]` to create an `IterableAPI`
   * The `apiKey` should correspond to the API key of your project in Iterable. If you'd like, you can specify a different `apiKey` depending on whether you're building in `DEBUG` or `PRODUCTION`, and point the SDK to the relevant Iterable project.
   * Ideally, you will call this from inside `application:didFinishLaunchingWithOptions:` and pass in `launchOptions`. This will let the SDK automatically track a push open for you if the application was launched from a remote Iterable push notification.