Functionality to add:

- Add hook_help()
	- Explain tab options: field_tabkey_tab_on to disable tag, field_tabkey_tab_title to change title
- Switch the tab_on and tab_title options away from fields. Maybe just add these options to every node edit form, and store in a new DB table?
- Add option to define the default tab
- Beef up the README
- Document API for hook_node_subpages_list()
- Should uninstall remove path aliases?



7.x-2.x
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* Add validation callback to validate the subpage config form: make sure a plugin is chosen and configured
* DOCUMENT how plugins should work