Added separated CSS file.
Namespaced the CSS selectors.
Allow selector for containerCls to be an ID, too.
Updated the jquery lib to the current version.
Added checked sign for checked option.
Improved unit test.
Added support for general selector for 'checkboxCls', and for adding
checked sign for selected option.
Added more functionality for toggling the selection of the main option.
Improved functionality as to selecting/deselecting the options.
Improved functionality of the dropdown checkbox.
Maintain selected icon on hovering a selected option.
Added callbacks for selecting/unselecting the options of the dropdown
checkbox component.
Reformat
Added  a function to check if the main option is selected.
Renamed class 'ddlcb-checked' to 'ddlcb-full-checked'.
Added functionality to display a partial checkmark icon on
selecting a secondary option.
Added maxNumberOfOptions, showComponentsStatusMessage,
componentsStatusMessageFormat, and selectedOptionsIndex.
Renamed the outward callback handlers.
Added a message section.
Added initialization function to component.