this change makes onChange callback to be always called in current Multiselect instance context

js/bootstrap-multiselect.js

@@ -39,6 +39,7 @@
         this.searchTimeout = null;
         
         this.options.multiple = this.$select.attr('multiple') == "multiple";
+        this.options.onChange = $.proxy(this.options.onChange, this);
         
         // Build select all if enabled.
         this.buildContainer();