one-way-select with prompt and includeBlank

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  
  options: ['A', 'B', 'C']
});

templates.application.hbs

{{one-way-select selectedValue
    options=options
    includeBlank=true
    prompt="Please select one:"
    update=(action (mut selectedValue))
}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1",
    "ember-one-way-controls": "2.0.0"
  }
}