title: Optional character in input mask
body: <p>How do I specify an optional character in an input mask?</p>
  
  <p>I found this masked input plugin <a href="http://digitalbush.com/projects/masked-input-plugin/" rel="noreferrer">http://digitalbush.com/projects/masked-input-plugin/</a> and these mask definitions.</p>
  
  <pre><code>$.mask.definitions['g']="[ ]";
  $.mask.definitions['h']="[aApP]";
  $.mask.definitions['i']="[mM]";
  $.mask.definitions['2']="[0-1]";
  $.mask.definitions['6']="[0-5]";
  new_mask = "29:69";
  $("#txtTime").mask(new_mask);
  </code></pre>
  
  <p>This defines an input mask for a 12 hour time format, e.g. 11:00.  I'd like to allow the user to specify only one digit for the "hour".  Instead of having to type 01:00, the user should be able to type 1:00.  How do I do that?</p>