title: Kendo Mask Custom Rule
body: <p>I've setup the following custom rule in a Kendo UI MaskedTextBox:</p>
  
  <pre><code>rules: {
      "~": /[0-9#]/
  }
  </code></pre>
  
  <p>I thought this would allow <code>0-9</code> or <code>#</code> in the field, but the mask text of <code>~</code> shows up and the masked box won't let me enter anything.  </p>
  
  <p>Where am I going wrong with the custom mask?  How do I configure a custom mask which will allow entry into the masked text box?</p>