title: Kingfisher and swift 3 - cannot set image with url
body: <p>Checking the documentation and the migration guide, I should be able to set a new image using this code: </p>
  
  <pre><code>imageView.kf.setImage(with:url ...) 
  </code></pre>
  
  <p>but actually I cannot find this method in the library, I only see: </p>
  
  <pre><code>imageView.kf.setImage(with:Resource... )
  </code></pre>
  
  <p>I don't know exactly how this resource shoud work though since I cannot find anything in the documentation. </p>