Add belongs_to tests for nil finder key case
Add belongs_to tests for nil finder key case

repinel/activeresource,peterjm/activeresource,delameko/activeresource,1776/activeresource,yui-knk/activeresource,SweeD/activeresource,rails/activeresource,Shopify/activeresource,om-nishu-trantor/activeresource,eileencodes/activeresource,chadzilla2080/activeresource,rjordan/activeresource,wyattisimo/activeresource,maclover7/activeresource