updated Readme

Author: yuzushioh

Readme.md

@@ -100,9 +100,11 @@ Then run `pod install` and that'll be 👌
 Add this to `Cartfile`
 
 ```
-github "RxSwiftCommunity/Action" ~> 2.1.1
+github "RxSwiftCommunity/Action" ~> 2.3.0
 ```
 
+If you are using RxSwift 3.2.0 or below, Use Action `~2.2.0` instead!
+
 then run
 
 ```