Refactor: Rename rsvp-routes.js
RSVP: Session defaults
RSVP: Food: .selected for last option
RSVP: Add adventure choices

Shirt, hosting, housing, volunteer
RSVP: Add canHaz to start page
RSVP: Use client-side session

Use a client-side session backed by
local storage, so that we can do
things press the back button without
losing UI state.

Also make defaults a little more
robust.