title: widget layout when using interact
body: <p>How can I use a container widget to control the layout while using interact?
  For instance, I'd like those 2 Select to be in a HBox.</p>
  
  <pre><code>from IPython.html import widgets
  from IPython.display import display
  
  def f(dl, ft):
      print dl, ft
  
  dlW = widgets.Select(options={str(k):k for k in  range(4)})
  ftW = widgets.Select(options={str(k):k for k in  'ABCD'})
  hbox=widgets.HBox([dlW, ftW])
  i = widgets.interact(f,
                   dl = dlW,
                   ft = ftW
                  )
  
  # display( hbox ) # &lt;-- commenting in makes the widget display twice
  </code></pre>