title: Using snapkit / autolayout with UIScrollView
body: <p>I have an app that will have a</p>
  
  <ul>
  <li>scrollView
  
  <ul>
  <li>contentView
  
  <ul>
  <li>chart</li>
  <li>buttons</li>
  <li>other stuff</li>
  </ul></li>
  </ul></li>
  </ul>
  
  <p>I tried constraining it like shown below, but I am missing a constraint and I can't find out what I need.</p>
  
  <pre><code>    self.view.addSubview(self.scrollView)
      self.scrollView.snp.makeConstraints { (make) in
          make.edges.equalTo(self.view)
      }
      let contentView = UIView()
  
      self.scrollView.addSubview(contentView)
      contentView.snp.makeConstraints { (make) in
          make.top.bottom.equalTo(self.scrollView)
          make.left.right.equalTo(self.view)
      }
      contentView.addSubview(self.chart)
      self.chart.snp.makeConstraints { (make) in
          // http://snapkit.io/docs/
          make.edges.equalTo(contentView).inset(UIEdgeInsets(top: 30, left: 0, bottom: 50, right: 0))
      }
  </code></pre>
  
  <p>where <code>scrollView = UIScrollView()</code></p>