title: How to disable the dropdown menu of select when the select only has one item
body: <p>I'm using 'select' widget from angularstrap.</p>
  
  <p>I'm wondering how to prevent the dropdown menu for the select only having one item. The only one item has been selected by default, how to prevent the click event on select to show the dropdown menu?</p>
  
  <p>Is it a missing feature of angularstrap?</p>
  
  <p>Check the <code>Single select</code> in <a href="http://plnkr.co/edit/NLYDffPWfg43w4YtYzix?p=preview" rel="nofollow">example</a></p>