Remove references to :show_zero_stock_products and :allow_backorders. Instead use can_supply to determine which variants to grey out.

Fixes #93
Fixes #104
merge from upstream
Merge branch '2-2-stable' of github.com:spree/spree_fancy into 2-2-stable
Change from using radio_button_tag to building up HTML so that id, name, and value aren't tied together anymore. The 'name' attribute is the string 'variant_id' since that's what the order populate controller wants. fixes #103