title: Plotly notebook mode with google colaboratory
body: <p>I am am trying out colaboratory with plotly notebook mode - I open a new notebook, copy and paste the following simple example from plotly's documentation, but don't see an output. There is a large blank in the output space where the plot whould normally be. </p>
  
  <p>This works fine in my local notebook (which is a newer version of plotly, but per their docs offline mode should work with the google colab version)
  Any ideas?</p>
  
  <pre><code>import plotly
  from plotly.graph_objs import Scatter, Layout
  
  plotly.offline.init_notebook_mode(connected=True)
  
  plotly.offline.iplot({
      "data": [Scatter(x=[1, 2, 3, 4], y=[4, 3, 2, 1])],
      "layout": Layout(title="hello world")
  })
  </code></pre>