function _buildCategoryList(){
            $("div[data-category-name]").each(function(i, item){
                var categoryName = $(item).data("categoryName");

                if(vars.categories.indexOf(categoryName) < 0){
                    vars.categories.push(categoryName);
                }
            });
        }
Build category list array from HTML data.
for check is new category, and Typeahead source of inputCategory.

@private