Added new list view widget and a new associated mixins directory that contains the selection mixin. Also added an example called master-detail that showcases the new list view and mixin.
Added a todo list.
Added more todo items.
Added break for while in populate() when called with iend None. Otherwise, it kept going beyond items count.
Changed selection_changed to observed_selection_changed to be explicit, to avoid confusion when the selection observer is itself a list (for cascading selection).
Added list_cascade example, to demonstrate a list that is itself a selection observer for another list.
Added missing str conversion, now that fruit example data is a list of ints.
Better class name. Cleaned up comments.
Removed unneeded property. Added reset of the list view items property when observed selection changes.
Changed SelectionSupport callback function to be handle_selection instead of select_object, because this can be select or deselect operation.
Added an initialize_selection callback when arranged_objects is reset.
Moved the initial set of arranged_objects to come after the associated callback is bound.
Added correct loop to unselect items if selection is single, but a multiple selection exists. Added todo comment and view lookup in update_selection().
Made deselected_color be the default background color for Button, in list_cascade example.
Fixed data entry.
Formatted master-detail example.
Added size_hint for master-detail example.
Renamed master_detail to list_master_detail so it shows up mainly pertaining to lists. Simplified master list.
Added sorting for list items.
Using handle_selection call instead of direct select call.