Use System.get instead of System.import

All of the modules we import should already be loaded, and we don't
want to ever attempt to import them anyway because we do not include a
Promise polyfill.

framework/core/views/app.blade.php

@@ -35,7 +35,7 @@
         };
 
         @foreach ($bootstrappers as $bootstrapper)
-          System.import('{{ $bootstrapper }}');
+          System.get('{{ $bootstrapper }}');
         @endforeach
 
         app.boot();