title: Swift 3.0 converting error fix
body: <p>I have a swift 2.2 project. 
  Now I upgraded it to Swift 3.0 but I have some errors.</p>
  
  <pre><code>open var gridClippingRect: CGRect
  {
      var contentRect = viewPortHandler?.contentRect ?? CGRect.zero
      contentRect.insetInPlace(dx: 0.0, dy: -(self.axis?.gridLineWidth ?? 0.0) / 2.0)
      return contentRect
  }
  </code></pre>
  
  <p>error: Value of type 'CGRect' has no member 'insetInPlace'</p>
  
  <p>How to fix this error?</p>