Use Ember.assign over Ember.merge in start-app.js
Use Ember.assign over Ember.merge in start-app.js

Context:
https://github.com/ember-cli/ember-cli/pull/5803
https://github.com/ember-cli/ember-cli/pull/5808
https://github.com/ember-cli/ember-cli/issues/6093

dockyard/ember-route-action-helper,dockyard/ember-route-action-helper