drawable tinting is done via app namespace

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/src/main/res/layout/lobby_view.xml

@@ -19,6 +19,7 @@
   -->
 
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:id="@+id/lobby_view"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
@@ -32,7 +33,7 @@
         android:layout_centerHorizontal="true"
         android:layout_margin="@dimen/margin_between_elements"
         android:src="@drawable/ic_room_service_black_24dp"
-        android:tint="@color/grey_600" />
+        app:tint="@color/grey_600" />
 
     <TextView
         android:id="@+id/lobby_text_view"