Add download badge

Author: Caitlin Bales (MSFT)

README.md

@@ -1,6 +1,9 @@
 # Preview Microsoft Graph SDK for Java
 *This SDK is currently in preview. Please continue to provide [feedback](https://github.com/microsoftgraph/msgraph-sdk-java/issues/new) as we iterate towards a production-supported library.*
 
+[ ![Download](https://api.bintray.com/packages/microsoftgraph/Maven/microsoft-graph/images/download.svg) ](https://bintray.com/microsoftgraph/Maven/microsoft-graph/_latestVersion)
+
+
 Get started with the Microsoft Graph SDK for Java by integrating the [Microsoft Graph API](https://graph.microsoft.io/en-us/getting-started) into your Java application!
 
 ## 1. Installation