Update bootstrap-multiselect.js

When using multiselect with Knockout to bind to an observableArray any changes to the array after the call to ko.applyBindings() are ignored. This patch rebuilds the mutliselect whenever a change is made to the ko.observableArray(). This is great for when a multiselect is loaded via a button click or dependent on other data such as choosing a state and then populating the multiselect with counties in that state.

The background for this fix can be seen here
https://github.com/davidstutz/bootstrap-multiselect/issues/214