Email producers with order/delivery instructions #275

Would be great to get a review of this as a sanity check.
There are nicer, more ruby-ish ways to check if an array is empty. I'd suggest `@order_cycle.distributors.any?` here. For non-arrays, use `my_thing.present?`. For the inverse, there is `my_thing.nil?`, `my_thing.blank?` for strings, `my_array.empty?`.