Resolve rails 4 dependencies
Remove attr_accessible from Product decorator
Clear out deprecated code in rails 4
Fix order inventory assembly after rails 4 upgrade

Probably some activerecord internals change that required us to reload
the object to get fresh associated records
Use allowed attributes in line item controllers
Use inventory_unit.line_item to fetch shipment line items

Resolve issue where a shipment item_cost would be 0 because it could not
find any line item associated with the shipment

Fixes #50
Fixing layout in product admin interface

Fixes #51
Support 2.1.0.beta
Remove 2-0-stable compatibility from master in README