lk | adds explanatory text to waiting list & disables mark_as_sold button for sold bikes, and removes unused columns

spec/models/bike_spec.rb

@@ -1,6 +1,18 @@
 require 'spec_helper'
 
 describe Bike do
+
+  describe "#sold?" do
+    it "returns true if the date_sold is present" do
+      bike = build :bike, date_sold: Time.zone.now
+      expect(bike.sold?).to be true
+    end
+    it "returns false if date_sold is not present" do
+      bike = build :bike
+      expect(bike.sold?).to be false
+    end
+  end
+
   describe "#post_to_bike_index" do
     it "does not calls BikeIndexLogger if no bike_index_id is present" do
       expect(BikeIndexLogger).not_to receive(:perform_async)