title: Polymer 1.x - cannot bind to href
body: <p>I would like to bind URL address to href.
  I tried the way recommended by polymer datasheet:</p>
  
  <pre><code>&lt;a href$="{{excelURL}}" class="btn btn--call-to-action" id="downloadBtn"&gt;Download excel&lt;/a&gt;
  </code></pre>
  
  <p>Anyway it is not working, and  element is not linked.Also without $ it is not working.  Normally other properties can be bind that way. Have you got an idea how to resolve it? </p>