Allow Spree::StockLocation and Spree::ShippingMethod to also be found by admin name.

Fix for 'undefined method with_indifferent_access for nil:NilClass' when not passing an address.

Add specs to finds stock location by name or admin name

Add specs to finds shipping method by name or admin name

Add specs to find stock location by name or admin name

Add specs to find stock location by name or admin name

Add specs to find shipping method by name or admin name

Fixes #33
Add resolution_path to customer returns

For customer returns that are not fully reimbursed, it is important to
provide a link to customer service agents notified through wombat. The
url is non-standard (as customer_returns are not intended to be scoped
to orders for the long term), so it is actually less brittle to build it
here.
Fixes #31