Realtime refactor: what do we need?

Just spit-balling -- do these seem right/doable? What else should we include?

- Add optional RT code to existing templates using variables or partials, not totally separate templates.

- Security: ability to select which models or fields get broadcast (e.g., don't want changes to users' passwords getting broadcast).

- Reuse server-side partials on client when rendering changes to RT data

- Bridge to allow model updates without having to do full REST posts. (Or maybe this should just be done via Ajax?)

- Server events from `geddy` global to allow startup without the hack after_start.js file.