title: Add padding around ASTextNode
body: <p>I am working with <em>AsyncDisplayKit</em> (for the first time) and have an <code>ASTextNode</code> inside a <code>ASCellNode</code>. I want to adding padding or an <em>inset</em> around the text inside the <code>ASTextNode</code>. I attempted to wrap it with a <code>ASDisplayNode</code> but whenever I calculated it's size in <code>calculateSizeThatFits:</code> it always returned 0. Any suggestions would be appreciated. The code that is in the <code>ASCellNode</code> subclass is:</p>
  
  <pre><code>- (CGSize)calculateSizeThatFits:(CGSize)constrainedSize
  {
      CGSize textSize = [self.commentNode measure:CGSizeMake(constrainedSize.width - kImageSize - kImageToCommentPadding - kCellPadding - kInnerPadding, constrainedSize.height)];
  
      return CGSizeMake(constrainedSize.width, textSize.height);
  }
  
  - (void)layout
  {
      self.imageNode.frame = CGRectMake(kCellPadding, kCellPadding, kImageSize, kImageSize);
      self.imageNode.layer.cornerRadius = kImageSize / 2.f;
      self.imageNode.layer.masksToBounds = YES;
      self.imageNode.layer.borderColor = [UIColor whiteColor].CGColor;
      self.imageNode.layer.borderWidth = 2.f;
  
      self.commentNode.backgroundColor = [UIColor whiteColor];
      self.commentNode.layer.cornerRadius = 8.f;
      self.commentNode.layer.masksToBounds = YES;
  
      CGSize textSize = self.commentNode.calculatedSize;
      self.commentNode.frame = CGRectMake(kCellPadding + kImageSize + kCellPadding, kCellPadding, textSize.width, textSize.height);
  }
  </code></pre>