* Add default stage_id logic that returns lowest sequence stage associated with
inheriting model and update unit tests accordingly
* Improve _read_group_stage_ids unit test
* Implement latest abstract model testing strategy
* Update depends to `base`
* Update priority selections to match Odoo guidelines
* Update comment block to triple double quotes
* Update `kanban_user_id` to `user_id` in code and view
* Update README to incorporate use of mode in example view
* Add Kanban-compatible stage model base.kanban.stage
* Add views, menu items, actions, and access controls needed to manage base.kanban.stage records
* Add abstract model base.kanban.abstract that other models can inherit from to gain Kanban stage functionality
* Add base Kanban view base_kanban_abstract_view_kanban, which can be customized as needed for use with models that inherit from base.kanban.abstract
* Add model base.kanban.abstract.tester, which is needed for base.kanban.abstract unit tests