skip over subscriptions with nil intervals
Adds billing address to subscription
Merge branch 'master' into feature/generate-order-service
Generate order service should rely on the stored billing address
Merge branch 'feature/generate-order-service' into feature/subscription-preorder

Conflicts:
	app/models/spree/subscription.rb
	spec/models/spree/subscription_spec.rb
	spec/services/generate_subscription_order_spec.rb