Cleaning up code in :item_before_change method on PaperTrail::Model::InstanceMethods; update CHANGELOG

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## 3.0.0 (Unreleased)
 
+  - [#280](https://github.com/airblade/paper_trail/pull/280) - Don't track virtual timestamp attributes.
   - [#278](https://github.com/airblade/paper_trail/issues/278)/[#272](https://github.com/airblade/paper_trail/issues/272) -
     Make RSpec and Cucumber helpers usable with [Spork](https://github.com/sporkrb/spork) and [Zeus](https://github.com/burke/zeus).
   - [#273](https://github.com/airblade/paper_trail/pull/273) - Make the `only` and `ignore` options accept `Hash` arguments;

lib/paper_trail/has_paper_trail.rb

@@ -268,10 +268,10 @@ module PaperTrail
         previous = self.dup
         # `dup` clears timestamps so we add them back.
         all_timestamp_attributes.each do |column|
-          previous[column] = send(column) if attributes.has_key?(column.to_s) && !send(column).nil?
+          previous[column] = send(column) if self.class.column_names.include?(column.to_s) and not send(column).nil?
         end
         previous.tap do |prev|
-          prev.id = id
+          prev.id = id # `dup` clears the `id` so we add that back
           changed_attributes.select { |k,v| self.class.column_names.include?(k) }.each { |attr, before| prev[attr] = before }
         end
       end