Improve waiting for window.onload

In case the window load event was fired before getting to the Ember
initializer, it would pause app loading indefinitely. This makes sure
that app loading is only paused, if there's still an event to wait for.

app/index.html

@@ -13,6 +13,12 @@
     <link rel="stylesheet" href="{{rootURL}}assets/kredits-web.css">
 
     {{content-for "head-footer"}}
+
+    <script>
+      window.addEventListener('load', function() {
+        window.windowLoadComplete = true;
+      });
+    </script>
   </head>
   <body>
     {{content-for "body"}}

app/initializers/defer-loading.js

@@ -6,9 +6,14 @@
 export default {
   name: 'defer-loading',
   initialize: function(application) {
+    // Load event already fired, so web3 should be loaded if available
+    if (window.windowLoadComplete) { return true; }
+
+    // Pause app loading
     application.deferReadiness();
 
     window.addEventListener('load', function() {
+      // Continue app loading
       application.advanceReadiness();
     });
   }