title: UI Bootstrap custom directive controller is not a function
body: <p>I want to use <a href="https://angular-ui.github.io/bootstrap/#/collapse" rel="nofollow">UI Bootstrap Collapse</a> in my custom directive <code>&lt;collapse&gt;</code></p>
  
  <p>However, I get this <code>Error: [ng:areq] Argument 'CollapseDemoCtrl' is not a function, got undefined</code></p>
  
  <p>Here is my <a href="http://plnkr.co/edit/Qx9xiFQMGXJ0w943v0UW?p=preview" rel="nofollow">Plunkr</a></p>
  
  <p>What am I doing wrong?</p>