title: Show legend and label axes in plotly 3D scatter plots
body: <p>Sorry for keeping you busy with plotly questions today. Here would be another one:
  How would I show the legend and axes labels on plotly's new 3D scatter plots? </p>
  
  <p>E.g., if I have the following scatter plot in 2D that produced everything fine, I added another dimension but the axes labels don't show anymore (see code below), and the same problem with the legend. Any tips? Thanks!</p>
  
  <p><img src="https://i.stack.imgur.com/ZEw7J.png" alt="enter image description here"></p>
  
  <p><img src="https://i.stack.imgur.com/tmGGo.png" alt="enter image description here"></p>
  
  <pre><code>traces = []
  
  for name in ('Iris-setosa', 'Iris-versicolor', 'Iris-virginica'):
  
      trace = Scatter3d(
          x=Y[y==name,0],
          y=Y[y==name,1],
          z=Y[y==name,2],
          mode='markers',
          name=name,
          marker=Marker(
              size=12,
              line=Line(
                  color='rgba(217, 217, 217, 0.14)',
                  width=0.5
              ),
              opacity=0.8
          )
  
      )
      traces.append(trace)
  
  
  data = Data(traces)
  layout = Layout(xaxis=XAxis(title='PC1'),
                  yaxis=YAxis(title='PC2'),
                  zaxis=ZAxis(title='PC3')
                  )
  fig = Figure(data=data, layout=layout)
  py.iplot(fig)
  </code></pre>