Update README.md

update to auth library notice

Author: DianeD

README.md

@@ -2,6 +2,9 @@
 
 ![Build Status](https://ricalo.visualstudio.com/_apis/public/build/definitions/06256fa7-d8e5-4ca0-8639-7c00eb6f1fe9/6/badge "Build Status")
 
+>**Note:** We're in the process of updating this sample to use the [recommended auth library](https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-v2-libraries#compatible-client-libraries) for Android apps.
+
+
 > **Building apps for enterprise customers?** Your app may not work if your enterprise customer turns on enterprise mobility security features like <a href="https://azure.microsoft.com/en-us/documentation/articles/active-directory-conditional-access-device-policies/" target="_newtab">conditional device access</a>. In this case, you may not know and your customers may experience errors. 
 
 > To support **all enterprise customers** across **all enterprise scenarios**, you must use the Azure AD endpoint and manage your apps using the [Azure Management Portal](https://aka.ms/aadapplist). For more information, see [Deciding between the Azure AD and Azure AD v2.0 endpoints](https://graph.microsoft.io/docs/authorization/auth_overview#deciding-between-azure-ad-and-the-v2-authentication-endpoint).