title: add "OK" button at bottom of the multi select dropdown bbotstrap
body: <p><a href="http://i.stack.imgur.com/gVjWp.png" rel="nofollow">bootstrap multiselect dropdown</a></p>
  
  <p>I want to add button at the bottom of the dropdown when I  scroll  drop-down button should be constant means fixed at the bottom.
  I am using <a href="http://davidstutz.github.io/bootstrap-multiselect/#getting-started" rel="nofollow">http://davidstutz.github.io/bootstrap-multiselect/#getting-started</a> link for the multi select dropdown.</p>