No longer need to check for CheckoutController + OrdersController

They are always present because spree_frontend is a dependency of this gem

Fixes #61
Fixed two deface warnings for the admin side

Fixes #63
Fix on_hand behavior to be compatible with changes in Spree master

Fixes #64
Dont automatically assign admin role.

Please assign admin role manually now:

user = User.find(...)
user.spree_roles << Spree::Role.find_by_name("admin")

Fixes #66
Use correct calculator within checkout_spec (shipping, rather than generic)
It's not necessary to create a variant for checkout_spec tests
Add User#admin? method.

Fixes #67
Fix require for BarAbility in Admin::UsersController spec
Correct shipping method used in promotion adjustment spec
Manually assign admin role within promotion_adjustment_spec tests

This is due to f5c812a09661925afe8f22cf81d3d17ad5836764
No need for test for Admin::OrdersController#show permissions any more

This was removed as part of the shipments changes on spree/spree master