bump version to 79

Change-Id: Iddd0dfeac73cd3c2cf897bded68a28d2ca9e4744

ring-android/app/src/main/AndroidManifest.xml

@@ -20,8 +20,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="cx.ring"
     android:installLocation="auto"
-    android:versionCode="78"
-    android:versionName="20170516">
+    android:versionCode="79"
+    android:versionName="20170531">
 
     <supports-screens
         android:anyDensity="true"