Fix README instructions to install Spree 1.3.3

Fixes #3671
Update :original SHA for promo_admin_tabs

Fixes #3670
Fixes #3700
Actually remove elements from the page when deleting them

This fixes a failing test in the 1-3-stable build: spec/requests/admin/products/edit/images_spec.rb
Only create new state_changes record if state actually changes
Only run `create_shipment!` when we really need it

In checkout_flow that would be only when order.total is zero and the
order has a shipping method

Fixes #3708
Be more precise about what state change events we care about when an order finalizes
Create payment method in customer_details_spec so it correctly transitions to payment state