title: How to make custom validator in Polymer for paper-input with type="number"?
body: <p>The following code works well if I don't have type="number".<br>
  With type="number" I can put "..." or "--123--" or "eee" without firing validation function..<br>
  How to fix that? <a href="http://plnkr.co/edit/9HXXM6" rel="nofollow">see Plunker example</a></p>
  
  <pre><code>&lt;script&gt;
      Polymer({
          is: 'custom-validator',
  
          behaviors: [
              Polymer.IronValidatorBehavior
          ]
   });
  
  &lt;/script&gt;
  
  &lt;dom-module id='validation-element'&gt;
    &lt;template&gt;
      &lt;custom-validator id="valid" validator-name="validator"&gt;&lt;/custom-validator&gt;
      &lt;paper-input type="number" auto-validate label='Amount' validator='validator' error-message="Invalid input!"&gt;
        &lt;div prefix&gt;$&lt;/div&gt;
      &lt;/paper-input&gt;
    &lt;/template&gt;
  &lt;/dom-module&gt;
  &lt;script&gt;
    Polymer({
      is: 'validation-element',
  
      validate: function(val) {
        var value = parseFloat(val);
        var isValid = !isNaN(value) &amp;&amp; typeof value === "number";
        console.log('validator', isValid);
  
        return isValid;
      },
  
      ready: function() {
        this.$.valid.validate = this.validate.bind(this);
      }
  
    });
  &lt;/script&gt;
  </code></pre>