title: RxSwift - mapping contentOffset of UITableView
body: <p>I'm trying to apply some logic to a component when a <code>UITableView</code> is scrolled, but I can't map the <code>contentOffset</code> property to return the <code>y</code>'s value.</p>
  
  <p>I'm testing like this but nothing happens:</p>
  
  <pre><code>table.rx.contentOffset.map {debugPrint($0)}
  </code></pre>
  
  <p>How can I do that?</p>