title: Matplotlib: "Unknown projection '3d'" error
body: <p>I just installed matplotlib and am trying to run one of there example scripts. However I run into the error detailed below. What am I doing wrong? </p>
  
  <pre><code>from mpl_toolkits.mplot3d import axes3d
  import matplotlib.pyplot as plt
  
  fig = plt.figure()
  ax = fig.gca(projection='3d')
  X, Y, Z = axes3d.get_test_data(0.05)
  cset = ax.contour(X, Y, Z, 16, extend3d=True)
  ax.clabel(cset, fontsize=9, inline=1)
  
  plt.show()
  </code></pre>
  
  <p>The error is </p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;string&gt;", line 245, in run_nodebug
    File "&lt;module1&gt;", line 5, in &lt;module&gt;
    File "C:\Python26\lib\site-packages\matplotlib\figure.py", line 945, in gca
      return self.add_subplot(111, **kwargs)
    File "C:\Python26\lib\site-packages\matplotlib\figure.py", line 677, in add_subplot
      projection_class = get_projection_class(projection)
    File "C:\Python26\lib\site-packages\matplotlib\projections\__init__.py", line 61, in get_projection_class
      raise ValueError("Unknown projection '%s'" % projection)
  ValueError: Unknown projection '3d'
  </code></pre>