title: Double indirection in data-binding. Interpolate string in a template
body: <p>I'm trying to resolve double binding in the link function of a directive:</p>
  
  <pre><code>scope.a = "surprise";
  scope.b = "{{ a }}";
  </code></pre>
  
  <p>the template  is <code>&lt;div&gt;{{ b }}&lt;/div&gt;</code></p>
  
  <p>it's rendered like <code>&lt;div&gt;{{ a }}&lt;/div&gt;</code></p>
  
  <p>is it possible to get the view to display <code>&lt;div&gt;surprise&lt;/div&gt;</code> ? 
  I've been trying to recompile the directive, but once <code>b</code> is binded, contents are a string and angularJS won't attempt any more to bind them.</p>