title: draw a border around subplots in matplotlib
body: <p>Anyone know how to draw a border around an individual subplot within a figure in matplotlib?  I'm using pyplot.</p>
  
  <p>eg:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  f = plt.figure()
  ax1 = f.add_subplot(211)
  ax2 = f.add_subplot(212)
  # ax1.set_edgecolor('black')
  </code></pre>
  
  <p>..but Axes objects have no 'edgecolor', and I can't seem to find a way to outline the plot from the figure level either.</p>
  
  <p>I'm actually wrapping mpl code and adding a wx UI with controls that I would like to have context depending on which subplot is selected.  i.e. User clicks on subplot within figure canvas -- subplot is 'selected' (has an outline drawn around it, ideally sawtooth) -- GUI updates to present controls to modify that specific subplot.</p>