[Breaking] Locale modules now extend from a Locale model (WIP)

[jasonmit]

• Add addMessages and addMessage to the intl service and which delegates to the locale module

this.intl.addMessage('en', 'greeting', 'hello');
this.intl.addMessage('fr', 'greeting', 'hello');

// will do a shallow merge based on feedback from @caridy
this.intl.addMessages('en' {
  greeting: 'hello',
  bye: 'goodbye'
});

This is extensible if you do not want your messages to hang off "messages" on the locale module. You can override addMessage/addMessages on the locale model.

• This locale model implements a accessor method so you can implement your own getter accessor logic.
  • This is the method invoked from intl-get and intl-get no longer acts on the service, but instead the active locale module instance.

It will resolve #24 #23 #18

All existing locale modules no longer can be POJOs and should extend from:

import Locale from 'ember-intl/models/locale’;

[jasonmit]

Thanks for adding the smoke tests @zeppelin, I've also added you as a contributor in package.json 👍

I fixed the failing test issues and will likely merge this shortly.