Display text in the editor based on the published appearance setting

[AngeloStavrow]

This is a stretch goal for an extension of #14, which only sets what font the Post will use after publishing. It'd be nice to show this change in the PostEditorView as well.

[thebaer]

As mentioned on our call, I think this is crucial for the 1.0 beta -- users will want to see the same fonts they're used to on the web. A minimum implementation might be:

• Use our "serif" font (Lora) for editor text on all local drafts (since this is the setting they publish with)
• For remote Posts, set the editor text font according to its appearance property

Beyond that, we can allow the user to set the post appearance, as outlined in #14.