#item_changes and #layout_changes are not documented #305
Description
When using nanoc live with a custom data source, the following warnings are printed:
Caution: Data source :character does not implement #item_changes; live compilation will not pick up changes in this data source.
Caution: Data source :character does not implement #layout_changes; live compilation will not pick up changes in this data source.
It would be good to document #item_changes and #layout_changes.