Update README.md

Added beta version

README.md

@@ -12,4 +12,6 @@ Easy starting points are also reviewing [pull requests](https://github.com/owncl
 
 **IRC channel:** [#owncloud-android](https://webchat.freenode.net/?channels=owncloud-android) on freenode IRC
 
+**Beta version** [beta version](https://github.com/owncloud/android/raw/beta/apks/latest.apk)
+
 **License:** [GPLv2](https://github.com/owncloud/android/blob/master/LICENSE.txt)