title: Why is my angularjs directive causing two-way binding to fail?
body: <p>I can't figure out why when my directive is enabled on an element, the two-way binding fails.</p>
  
  <p>Consider this <a href="http://plnkr.co/edit/yfCPQxsNWo4uIApwuv5H?p=preview" rel="nofollow">plunkr</a></p>
  
  <p>On the first  removing the <code>tooltip={{input1Error}}</code> makes the <code>input1</code> variable update as soon as you type in a valid email.</p>
  
  <p>When <code>tooltip={{input1Error}}</code> is added, when typing in a valid email, the <code>input1</code> model is never updated.</p>
  
  <p>What am I missing?</p>