Update README and CHANGELOG regarding merge of #507

CHANGELOG.md

@@ -9,6 +9,8 @@ PaperTrail::Rails::Engine.eager_load!
 
 If you depend on the `RSpec` or `Cucumber` helpers, you will need to [manually load them into your test helper](https://github.com/airblade/paper_trail#testing).
 
+  - [#507](https://github.com/airblade/paper_trail/pull/507) - Support for opting out of saving changesets on models by choice
+    when the `object_changes` column exists on the default `versions` table.
   - [#500](https://github.com/airblade/paper_trail/pull/500) - Support for passing `on: []` as an argument, with only manual
     versioning via calls to `touch_with_version`
   - [#494](https://github.com/airblade/paper_trail/issues/494) - The install generator will warn the user if the migration they are

README.md

@@ -844,6 +844,7 @@ For diffing two ActiveRecord objects:
 * [Jeremy Weiskotten's PaperTrail fork](http://github.com/jeremyw/paper_trail/blob/master/lib/paper_trail/has_paper_trail.rb#L151-156): uses ActiveSupport's diff to return an array of hashes of the changes.
 * [activerecord-diff](http://github.com/tim/activerecord-diff): rather like ActiveRecord::Dirty but also allows you to specify which columns to compare.
 
+If you wish to selectively record changes for some models but not others you can opt out of recording changes by passing `:save_changes => false` to your `has_paper_trail` method declaration.
 
 ## Turning PaperTrail Off/On