Adding prefix to 'collapse' for Twitter Bootstrap compatibility.

css/multi-select.css

@@ -32,7 +32,7 @@
   width: 170px;
   height: 200px;
   padding: 1px 0px;
-  
+
   overflow-y: auto;
 
 }
@@ -62,7 +62,7 @@
   color: #999;
 }
 
-.ms-container .ms-optgroup-label.collapse{
+.ms-container .ms-optgroup-label.ms-collapse{
   background-image: url('../img/minus.png');
 }
 
@@ -75,4 +75,4 @@
 
 .ms-container .ms-selection li:not(.disabled):hover{
   background: #eee url('../img/delete.png') no-repeat 3px 3px;
-}
+}

js/application.js

@@ -4,12 +4,12 @@
     $('.multiselect').multiSelect({});
     $('#ms-optgroup .ms-selectable, #ms-outsideCountries .ms-selectable').find('li.ms-elem-selectable').hide();
     $('.ms-optgroup-label').click(function(){
-      if ($(this).hasClass('collapse')){
+      if ($(this).hasClass('ms-collapse')){
         $(this).nextAll('li').hide();
-        $(this).removeClass('collapse'); 
+        $(this).removeClass('ms-collapse'); 
       } else {
         $(this).nextAll('li:not(.ms-selected)').show();
-        $(this).addClass('collapse');
+        $(this).addClass('ms-collapse');
       }
     });
 
@@ -83,4 +83,4 @@
       return false;
     });
   });
-})(jQuery)
+})(jQuery)

js/jquery.multi-select.js

@@ -184,7 +184,7 @@
 
         var parentOptgroup = selectableLi.parent('.ms-optgroup');
         if (parentOptgroup.length > 0){
-          parentOptgroup.children('.ms-optgroup-label').addClass('collapse').show();
+          parentOptgroup.children('.ms-optgroup-label').addClass('ms-collapse').show();
           parentOptgroup.children('.ms-elem-selectable:not(.ms-selected)').show();
         }
         selectedOption.removeAttr('selected');