Support ES6 syntax

[tricknotes]

Abstract

We can use es6 syntax on asset pipeline.
This way is the same as ember-cli .

The setting specified ember-rails is the followings:

• my-app.js.es6

  //= require ember-rails/application
  //= require_tree
  //= require_self
  
  import App from 'ember-rails/application';
  
  App.create();

• application.js

  // = require ./my-app
  
  require('my-app');

I think the following benefits are there for ember-rails users:

• It supports ES6 (current Ember way) in ember-rails.
• It helps migrating from ember-rails ls to Ember CLI

TODO

• Support es6 module syntax
• Support generator option javascript-engine=es6
• Add test
• Write how to use es6 module syntax to README
• Write about how to use multiple app
• Change ES6 transpiler

[tricknotes]

Now this PR is ready to review.

@stefanpenner @rwjblue
Could you give me a feedback +1/-1 ?

[ashrafmajdee]

+1

[bradleypriest]

Awesome, do you think we'll be able to support .js.coffee.es6 or .js.es6.coffee at some point as well?

[tricknotes]

Yes, It is important but now it doesn't be supported.
I'll support it at some early date.

[mmun]

Looking forward to seeing this land! 👍

[stefanpenner]

lets try to align this with ember-cli's conventions, all files/folders in the app are dasherized

[tricknotes]

agreed 😉

[tricknotes]

I'm now working on another branch because I have to consider implementation carefully.
When it is decided, I'll update this PR.

[tricknotes]

Updated to add the following to this PR's description:

I think the following benefits are there for ember-rails users:

• It supports ES6 (current Ember way) in ember-rails.
• It helps migrating from ember-rails ls to Ember CLI

[tricknotes]

All TODO things are done.

@stefanpenner @rwjblue
Could you review again?

[tulios]

Hi @tricknotes, awesome work! Do you have a fork with this change? I would like to try, this definitely will help to migrate to ember-cli.

[mufid]

Any update for this?