title: Center a colormap around 0 in Mayavi
body: <p>I'm plotting a point cloud and coloring by residual error. I'd like the colormap to remain centered on 0, so that 0 error is white.</p>
  
  <p>I see <a href="https://stackoverflow.com/questions/16781255/automatic-construction-of-a-colormap-around-the-value-zero">answers for matplotlib</a>. What about Mayavi?</p>
  
  <pre><code>from mayavi import mlab
  mlab.points3d(x, y, z, e, colormap='RdBu')
  </code></pre>