title: How to check iOS version?
body: <p>I want to check if the <code>iOS</code> version of the device is greater than <code>3.1.3</code>
  I tried things like:</p>
  
  <pre><code>[[UIDevice currentDevice].systemVersion floatValue]
  </code></pre>
  
  <p>but it does not work, I just want a:</p>
  
  <pre><code>if (version &gt; 3.1.3) { }
  </code></pre>
  
  <p>How can I achieve this?</p>