Use URL param for registration flow

So, soon, the registration flow will use URL params and redirections
instead of session variables. Here's how:

  GET /registrations/new
    -> /people/:id/edit if needs to input personal details
    -> /people/:id/waiver if hasn't signed waiver

Each of those steps will either (by default) redirect to the GET version
of the same thing (i.e. #new) or if ?next=registration param is passed
it, it will redirect back to /registrations/new, so the registration
process can again redirect the user accordingly.
Tidy up the registration process

This glues the different parts together via the ?next=registration
param. So despite what steps we add to the registration flow, as long as
RegistrationController redirects you to the proper step, you'll follow
the flow all right.
Remove rails junk from README
Move Game#can_register? before filter to ApplicationController
Move the waiver validations to the waivers
Write a test for the final step in the registration process
Remove caching and actually include needed associations

So, this improves GamesController#show's rendering speed quite a bit.
The N+1's are gone, and so is the caching. On my laptop, rendering 500
players takes about 5 seconds, with about 3.4 seconds in views and 1.6
getting lost in the rails ether (only 23.7ms in ActiveRecord).

Maybe a bit too slow to remain without caching. This uses
ActionController::ConditionalGet#stale? to return a cached version of a
page if the Game instance hasn't changed. Although the game instance
changes every minute during the game, maybe nginx as a reverse proxy can
roll together everyone's requests...?

Conflicts:
	app/controllers/games_controller.rb
	app/models/registration.rb
	app/views/games/_gamestats.html.haml
	app/views/games/_scoreboard.html.haml
	app/views/games/show.html.haml
	lib/update_game_state.rb
WIP Achievements

Conflicts:
	Gemfile
	Gemfile.lock
	db/schema.rb
Add some fragment caching back in to GameController#show
Caching and general cleanup on GameController#show

Conflicts:
	app/models/registration.rb
Move JS to the footer

Get down there where you belong!
Changes to JS load order

Plus pull in a CDN version of Backbone!
Asset Pipeline and Autocomplete refactor

So I wanted to rip out jQuery UI because it's big and only used for the
autocomplete box. So then I ripped out the autocomplete box and built a
new one with Backbone. But then everything is bad because it's in
public/ and doesn't use the assets pipeline. So then I moved everything
around and probably broke things in a bad way.

Anyway, here it is.

Conflicts:
	Gemfile.lock
Clean up application styles

Conflicts:
	app/views/index/_adminnavigation.html.haml
Refactor the JS stuff

Ideally I want the player-select dropdown to be not tied to the context
in which it is displayed (similiar to the old API). So it should trigger
an `autocomplete:selected` event when the admin picks a player and then
the enclosing view knows what to do with it.
Sort the autocomplete list better

It now will assume you meant the person's first name.
Move jQuery.countdown to proper asset location
Use the asset manifest for JS files