title: jQuery counter to count up to a target number
body: <p>I'm trying to find out if anyone knows about an already existing jQuery plugin that will count up to a target number at a specified speed.</p>
  
  <p>For example, take a look at Google's number of MB of free storage on the <a href="http://gmail.com" rel="noreferrer">Gmail homepage</a>, under the heading that reads "Lots of space". It has a starting number in a <code>&lt;span&gt;</code> tag, and slowly counts upward every second.</p>
  
  <p>I'm looking for something similar, but I'd like to be able to specify:</p>
  
  <ul>
  <li>The start number</li>
  <li>The end number</li>
  <li>The amount of time it should take to get from start to end.</li>
  <li>A custom callback function that can execute when a counter is finished.</li>
  </ul>