def listings(state = nil, options = {})
      state = state ? {:state => state} : {}
      Listing.find_all_by_shop_id(id, state.merge(options).merge(oauth))
    end
def listings(state = nil, options = {})
      state = state ? {:state => state} : {}
      Listing.find_all_by_shop_id(id, state.merge(options).merge(oauth))
    end
The collection of listings associated with this shop