Remove some global refs to window.events

// FREEBIE

js/background.js

@@ -86,9 +86,9 @@
             openInbox();
         }
 
-        Whisper.WallClockListener.init();
+        Whisper.WallClockListener.init(events);
-        Whisper.RotateSignedPreKeyListener.init();
+        Whisper.RotateSignedPreKeyListener.init(events);
-        Whisper.ExpiringMessagesListener.init();
+        Whisper.ExpiringMessagesListener.init(events);
     });
 
     window.getSyncRequest = function() {

js/expiring_messages.js

@@ -37,9 +37,9 @@
     }
 
     Whisper.ExpiringMessagesListener = {
-        init: function() {
+        init: function(events) {
             checkExpiringMessages();
-            window.events.on('timetravel', checkExpiringMessages);
+            events.on('timetravel', checkExpiringMessages);
         },
         update: checkExpiringMessages
     };

js/rotate_signed_prekey_listener.js

@@ -46,15 +46,15 @@
     }
 
     Whisper.RotateSignedPreKeyListener = {
-        init: function() {
+        init: function(events) {
             if (Whisper.Registration.isDone()) {
                 setTimeoutForNextRun();
             }
-            window.events.on('registration_done', function() {
+            events.on('registration_done', function() {
                 scheduleNextRotation();
                 setTimeoutForNextRun();
             });
-            window.events.on('timetravel', function() {
+            events.on('timetravel', function() {
                 if (Whisper.Registration.isDone()) {
                     setTimeoutForNextRun();
                 }

js/wall_clock_listener.js

@@ -8,17 +8,19 @@
 
     var lastTime;
     var interval = 1000;
+    var events;
     function checkTime() {
       var currentTime = Date.now();
       if (currentTime > (lastTime + interval * 2)) {
           console.log('time travel detected!');
-          window.events.trigger('timetravel');
+          events.trigger('timetravel');
       }
       lastTime = currentTime;
     }
 
     Whisper.WallClockListener = {
-      init: function() {
+      init: function(_events) {
+          events = _events;
           lastTime = Date.now();
           setInterval(checkTime, 1000);
       }