Make sure that the images aren't CMYK. [Fixes #3104]
No need to pass option on spree.promo initializer

For some reason this was making the calculator.shipping_methods nil in
the spree app initializer. It prevented users from adding their own
calculators with code like:

  Rails.application.config.spree.calculators.shipping_methods << CustomUserClass

Fixes #3118
Deprecate Order#shipment as split_shipments makes it less relevant
Stop using deprecated Order#shipment method in OrderInventory spec
Scope shipping rates as per display_on

As shipping method rates set to appear only in backend should not be
displayed in frontend as well

[Fixes #3119]