Upgrade to latest Ember, etc.

testem.js

@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = {
   test_page: 'tests/index.html?hidepassed',
   disable_watching: true,
@@ -7,13 +9,13 @@ module.exports = {
   launch_in_dev: [
     'Chrome'
   ],
+  browser_start_timeout: 120,
   browser_args: {
     Chrome: {
       ci: [
         // --no-sandbox is needed when running Chrome inside a container
         process.env.CI ? '--no-sandbox' : null,
         '--headless',
-        '--disable-gpu',
         '--disable-dev-shm-usage',
         '--disable-software-rasterizer',
         '--mute-audio',