Don't autosave on focus-in to editor

Closes #4321
- Added a PostTitleInputComponent that sets its value to "(Untitled)" if it has no value on focusOut, and selects its text if its text is "(Untitled)" on a click.
- Removed autoSaveNew action firing onFocusIn of the markdown editor
- emberified the gh-trim-focus-input
- editor-base-controller is no longer responsible for setting a default title (horay!)
```
focusOut: function (event) {
        this._super(event);
        if (!this.get('value')) {
            var self = this;
            this.setTitle = Ember.run.once(this, function () {
                self.set('value', '(Untitled)');
            });
        }
    },
    dontSetTitle: function () {
        if (this.setTitle) {
            Ember.run.cancel(this.setTitle);
        }
    }.on('willDestroyElement'),
```

Delaying setting the title to `(Untitled)` until the next tick works like a bloody charm!