def update_version
      return create_version unless v = versions.last
      v.modifications_will_change!
      v.update_attribute(:modifications, v.changes.append_changes(version_changes))
      reset_version_changes
      reset_version
    end
def update_version
      return create_version unless v = versions.last
      v.modifications_will_change!
      v.update_attribute(:modifications, v.changes.append_changes(version_changes))
      reset_version_changes
      reset_version
    end
Updates the last version's changes by appending the current version changes.