Use ES7 features

[holandes22]

• async/await http://karolgalanciak.com/blog/2015/12/18/ember-and-es7-async-slash-await/
• Decorators in CPs https://github.com/rwjblue/ember-computed-decorators

[holandes22]

Tried but there are still several issues with linting, deferring for after the first public release