Update README.md

Change:
1. Description DUO process;
2. Change composer dependency to release version (not dev version).

README.md

@@ -5,7 +5,7 @@ This is a Roundcube webmail plugin that enables [Duo Security](https://duo.com)
 
 ![image](https://duo.com/assets/img/documentation/duoweb/websdk_network_diagram.png)
 
-It creates an additional page after successful username/password authentication that requires a 2nd Factor of Authentication using Duo Security (push, sms, call, hardware token code).
+It redirect to additional page after successful username/password authentication that requires a 2nd Factor of Authentication using Duo Security (push, sms, call, hardware token code).
 
 INSTALLATION
 ============
@@ -15,7 +15,7 @@ Run `$ composer update`
 
 Run `$ composer dumpautoload`
 
-Run `$ composer require lmr/duo_auth dev-master`
+Run `$ composer require "lmr/duo_auth:^1.0.9"`
 
 CONFIGURATION
 =============