title: jQuery live check input changes
body: <p>I am stuck with a new code, and I seek a smart one-way efficient solution. 
  I want to accomplish something similar to Twitter, Let's say we have two
  inputs of type=Text, and once one changes we either removeAttr("disabled", "disables"); or attr("disabled", "disabled"), I know this is easy to accomplish when checking one field, but lets say I changed on Field, and next I change the other field, and all of the sudden I decide to change one of them back, or vice versa or both back to previous values, so that the submit button changes between disabled/enabled. </p>
  
  <p>Here's my jsfiddle: <a href="http://jsfiddle.net/Xu9XH/" rel="nofollow">http://jsfiddle.net/Xu9XH/</a></p>
  
  <pre><code>&lt;input type="text" value="Carl" name="first_name" maxlength="15" id="firstname" /&gt;
  &lt;input type="text" value="Johnson" name="last_name" maxlength="15" id="lastname" /&gt;
  &lt;br /&gt;&lt;br /&gt;
  &lt;button id="senddata" disabled="" type="submit"&gt;Submit&lt;/button&gt;
  </code></pre>