title: IOS using SDWebImage gives no setImageWithURL method error
body: <p>Hi I am trying to use SDWebImage library for my project. I copied all the files. I have imported <code>#import "UIImageView+WebCache.h"</code> But when I tried to use </p>
  
  <pre><code>[cell.mediaImg setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
                 placeholderImage:[UIImage imageNamed:@"placeholder.png"]];
  </code></pre>
  
  <p>it gives me error</p>
  
  <pre><code>No visible @interface for 'UIImageView' declares the selector 'setImageWithURL:placeholderImage:'
  </code></pre>
  
  <p>So I am doing anything wrong. What else things I have to use. Need some help. Thank you.</p>