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

app/models/bike.rb

@@ -25,6 +25,10 @@ class Bike < ActiveRecord::Base
     ]
   end
 
+  def sold?
+    date_sold.present?
+  end
+
   def name
     self.color + " " + self.brand + ' ' + self.model + " (" + self.log_number.to_s + ")"
   end