title: Angular modal-backdrop issue
body: <p>I am using <code>angular-bootstrap</code> modal but I have an issue with modal-backdrop. I am new to <code>angular-bootstrap</code>, and I hope anyone can help me.</p>
  
  <p>When I click on modal-backdrop it's hiding the modal popup, but I would like to keep the modal-backdrop until click cancel.</p>
  
  <p><a href="http://plnkr.co/edit/YPESA3?p=preview" rel="noreferrer">modal popup code is here</a></p>
  
  <p>any one please suggest the solution for this. </p>
  
  <p>Thanks</p>