Update README.md

README.md

@@ -15,7 +15,7 @@ This is the official node.js module for sending notifications with node.js with
 Recent version v6 can be unstable, its recommended to use version `v5.7.0`. We are actively working on making v6 stable and will be updating the README accordingly soon.
 
 ```bash
-npm install @trycourier/courier
+npm install @trycourier/courier@5.7.0
 ```
 
 ## Requirements