getting options dynamically and other slight gulpfile changes

NOTE: after updating the options dynamically, the following 3 options
were removed:

- includeSelectAllDivider
- includeSelectAllIfMoreThan
- templates

and the following 7 were added:

- allSelectedText
- disableIfEmpty
- enableClickableOptGroups
- nSelectedText
- onDropdownHidden
- onDropdownShown
- selectAllName