title: kendo.tostring does not format number when value is string
body: <p>I am using <code>kendo.toString()</code> method to format string as <a href="http://docs.telerik.com/kendo-ui/framework/globalization/numberformatting#types-of-number-formats" rel="nofollow noreferrer">documented here</a>
  So for example</p>
  
  <pre><code>   kendo.culture("en-US");
     kendo.toString(5000, "n")
  </code></pre>
  
  <p>returns <code>5,000</code></p>
  
  <p>However if i pass string parameter then it does not work</p>
  
  <pre><code>   kendo.culture("en-US");
     kendo.toString("5000", "n")
  </code></pre>
  
  <p>returns <code>5000</code></p>
  
  <p><a href="https://jsfiddle.net/cpcz3478/1/" rel="nofollow noreferrer">JSFiddle</a></p>