feat(dropdown): improve accessibility in relation to search dropdown

in case of using the <label> element before a search dropdown to improove accessibility

id of module is used to add an unique id to this very label
a reference to this label is made via the attribut "labelledby"
see w3.org/WAI/tutorials/forms/labels

Author: Inselhopper

src/definitions/modules/dropdown.js

@@ -111,6 +111,7 @@ $.fn.dropdown = function(parameters) {
               module.error(error.noNormalize, element);
             }
 
+            module.create.id();
             module.setup.layout();
 
             if(settings.values) {
@@ -124,7 +125,6 @@ $.fn.dropdown = function(parameters) {
             module.save.defaults();
             module.restore.selected();
 
-            module.create.id();
             module.bind.events();
 
             module.observeChanges();
@@ -366,11 +366,20 @@ $.fn.dropdown = function(parameters) {
             }
             if( module.is.search() && !module.has.search() ) {
               module.verbose('Adding search input');
+              var
+                  labelNode = $module.prev('label')
+              ;
               $search = $('<input />')
                 .addClass(className.search)
                 .prop('autocomplete', module.is.chrome() ? 'fomantic-search' : 'off')
-                .insertBefore($text)
               ;
+              if (labelNode.length) {
+                if (!labelNode.attr('id')) {
+                  labelNode.attr('id', module.get.id() + '_formLabel');
+                }
+                $search.attr('aria-labelledby', labelNode.attr('id'));
+              }
+              $search.insertBefore($text);
             }
             if( module.is.multiple() && module.is.searchSelection() && !module.has.sizer()) {
               module.create.sizer();