title: Polymer: multiple filters in template dom-repeat
body: <p>I have a simple dom repeat like this:</p>
  
  <pre><code>&lt;template is="dom-repeat" items="{{projects}}" as="project" filter="{{computeFilter(searchString)}}"&gt;
  [[project.name]] - [[project.number]]
  &lt;/template&gt;
  
  &lt;paper-input name="filter-name" label="Filter by project name" value="{{searchString}}"&gt;&lt;/paper-input&gt;
  </code></pre>
  
  <p>And there is a function that filters the projects by name:</p>
  
  <pre><code>computeFilter: function(keyword) {
    if (!keyword) {
      return null;
    } else {
      keyword = keyword.toLowerCase();
      return function(project) {
        var name = project.name.toLowerCase();
        return (name.indexOf(keyword) != -1);
      };
    }
  }
  </code></pre>
  
  <p>All good. Now, how would I go about adding another filter, if for example I'd also like ot filter by project number?</p>
  
  <p>I would have another paper button binding to {{searchString2}}, but then how would I link this to a filter - in other words, how can I set up multiple filters on a dom-repeat?</p>