Fix deselect and select option when using options with empty values
Allow to configure the attr used for button title
Merge branch 'deselect_select'
Merge branch 'button_title_attr'
Add an option to build optgroups with additional checkboxes and click all events
Apply commentation from @philfreo
Only try to select associated option for an checkbox select event when not changing state for an optgroup
Merge branch 'option_groups'