Button now inherits ID from select Fixes #641

Appends "_ms" to the inherited ID.

Updated unit tests with new attribute and updated minified code.

Author: mlh758

src/jquery.multiselect.js

@@ -60,7 +60,7 @@
       var button = (this.button = $('<button type="button"><span class="ui-icon ui-icon-triangle-1-s"></span></button>'))
         .addClass('ui-multiselect ui-widget ui-state-default ui-corner-all')
         .addClass(o.classes)
-        .attr({ 'title':el.attr('title'), 'tabIndex':el.attr('tabIndex') })
+        .attr({ 'title':el.attr('title'), 'tabIndex':el.attr('tabIndex'), 'id': el.attr('id') + '_ms' })
         .prop('aria-haspopup', true)
         .insertAfter(el),