Added in_after_callback argument to save_with_version

[denisahearn]

My application calls PaperTrail::RecordTrail#save_with_version in an after callback. The version record that this method creates does not record the current changes on the object being tracked. I found the cause in the PaperTrail::Events::Base#load_changes_in_latest_version method, which only uses @record.saved_changes when @in_after_callback is true. Unfortunately I don't currently see a way to make @in_after_callback == true when using save_with_version.

This pull request adds an in_after_callback argument to the PaperTrail::RecordTrail#save_with_version method, to allow the caller to indicate if this method is being called during an after callback. The argument defaults to false when not provided.

Check the following boxes:

• Wrote good commit messages.
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new
  code introduces user-observable changes.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.

[jaredbeck]

Hi Denis, thanks for the contribution. I'm not sure how many people will use this new feature, but there aren't really any good alternatives that I can think of. It's a good PR too :) You've ticked all the boxes.