Preview doesn't update with keys

[ryanbugden]

Reproduce:

• Set up some sort of preview, don't Apply.
• Select some points of the drawing, use Scale tool to make some sort of change.
• Hit Enter to commit and exit the Scale tool.
• Use arrow keys to move around points. Preview doesn't update after these arrow-key changes.

[ryanbugden]

Just doesn't respond to keys...

Need to find a way to instantiate a glyph editor subscriber separate from the UI class (otherwise, it will open one per UFO).

In the meantime, I will use glyphEditorDidKeyDown, which for some reason RoboFontSubscribers look at.