fix(RingOverlay): puts the "ring overlay" back below the toolbars

css/_variables.scss

 $toolbarZ: 900;
 $overlayZ: 902;
 $notificationZ: 1012;
+$ringingZ: 800;
 
 /**
  * Font Colors TODO: Change colors when general dialogs are implemented.

css/ringing/_ringing.scss

     width: 100%;
     height: 100%;
     position: fixed;
-    z-index: $overlayZ;
+    z-index: $ringingZ;
     background: linear-gradient(transparent, #000);
     opacity: 0.8;