Update README.md

README.md

@@ -22,7 +22,7 @@ All you have to do is start the webserver and then visit it at it's domain name.
 ## Install
 
 ```
-npm install --save letsencrypt-express
+npm install --save letsencrypt-express@1.x
 ```
 
 *Pay no attention to the man behind the curtain.* (just ignore that the name of the module is letsencrypt-express)