RB.ReviewablePageView has been working with a model, taking in all

attribute data as view options and handling logic internally. This means

we can't do things like listen for attribute changes, and some future

work for dynamic updates is not very clean when contained solely in the

view.
This change introduces the RB.ReviewablePage and

RB.ReviewRequestPage models. RB.ReviewablePage is now responsible

for storing and transforming all the data formerly passed in as view

options (such as the editor state and review request data), and sets up

the related objects needed by other models and views.
In upcoming changes, the models will take on more responsibilities

needed for dynamic updating of pages.

Unit tests pass.
Tested all actions on the review request, diff viewer, and review UI pages.
Tested editing review request fields and publishing changes.
Tested viewing diffs, changing pages, and changing revisions.
Tested commenting on diffs and images.
Tested adding general comments.
Tested the Ship It button.
Tested opening and publishing the review dialog.