Implement Notifications for Ember

closes #2417
- Adds Notification(s)Component
- Render notifications in application.hbs
- Adds handleError in application route
Merge pull request #2472 from halfdan/ember-notifications-2417

[Ember.js] Implement Notifications for Ember
Create Post Settings Menu and its functionality on the Post controller.

closes #2419
- Added blur-text-field component, which fires actions on focusOut
- Added utils/date-formatting for moment & date functionality  consolidation
- Added functionality to PostsPostController
- Added fixtures: posts/3 & posts/4, posts/slug/test%20title/
- Added Post model saving
- Set posts.post as controller for EditorRoute
- Added PostSettingsMenuView and template
- Added "showErrors" convenience method to notifications