Added s3 support. Fixes #1

Removed strong params

Added basic test coverage of s3 in digitals_controller

Conflicts:
	app/controllers/spree/admin/digitals_controller.rb
	app/controllers/spree/admin/orders_controller_decorator.rb
	app/controllers/spree/digitals_controller.rb
	app/models/spree/digital.rb
	spec/controllers/digitals_controller_spec.rb