title: Convert System.DateTime to NodaTime.ZonedDateTime
body: <p>I have a <code>System.DateTime</code> which is already in a specific timezone but does not specify a <code>DateTime.Kind</code>, and a string that represents an IANA timezone. I want to convert this to a <code>NodaTime.ZonedDateTime</code>.</p>
  
  <p>For example:</p>
  
  <pre><code>var original = new DateTime(2016, 1, 1, 12, 0, 0);
  var timezone = "America/Chicago";
  </code></pre>
  
  <p>I want a <code>ZonedDateTime</code> that represents 01/01/2016 - 12PM in Chicago time. How do I do this?</p>