Idea: React-style state model view rendering

Per [my article posted this morning](http://jamonholmgren.com/rubymotion-react-pattern/), I'd like to discuss bringing in a React-style `set_state` method on `PM::Screen` and providing a `render` (or `layout`) method in the RMQ stylesheet.

Other things to discuss:
- **View hierarchy diffing** -- is it worthwhile from a performance standpoint? Updating UI elements in RMQ is super fast, so it might not make sense.
- **Components** -- should we have some analog to React.js components?
- **Table screens / collection screens** -- this should be easy(ish) with `update_table_data` and the like, but we should discuss.
- **Animations** -- animating between state changes

Lastly, I have to thanks @twerth for building RMQ -- makes this sort of thing so easy. :-)

Start by reading the linked article and the existing PM::Screen and RMQ stylesheet APIs, including update_table_data. The issue is a discussion of state updates, rendering, diffing, components, tables, and animations; it is done only when the intended scope and design are agreed.

Written by the indexing model from the issue text.