title: How to add validation attributes to md-autocomplete angular material directive
body: <p>I'm using version 0.7.1 of angular material. I'm using the autocomplete as described here: 
  <a href="https://material.angularjs.org/#/demo/material.components.autocomplete" rel="noreferrer">Autocomplete demo</a></p>
  
  <p>However, it doesn't seem to support validation logic, even though it generates a textarea: 
  <a href="https://material.angularjs.org/#/api/material.components.autocomplete/directive/mdAutocomplete" rel="noreferrer">Autocomplete directive documentation</a></p>
  
  <p>I imagine that I can add logic in the querySearch function to switch ng-valid to ng-invalid. Is this correct? If this is the case, then I need a handle on the md-autocomplete, but this is difficult, because the name attribute gets removed. </p>