ember-cli-nwjs doesn't work with ES7 async

Hello,

getting following error:

"Uncaught ReferenceError: regeneratorRuntime is not defined",

```
async start(){
    try {
       let response = await this.get('sync').request(json);
....
```

In ember-cli-build.js I am using:

`var app = new EmberApp(defaults, {
    babel: {
      includePolyfill: true
    }
  });`

On browser works fine
