title: How to shrink a subplot colorbar
body: <p>starting from this code:</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as pl
  import matplotlib 
  from matplotlib.gridspec import GridSpec 
  
  x=np.linspace(0.0,1.0,100)
  y=np.linspace(0.0,1.0,100)
  xv,yv=np.meshgrid(x,y)
  
  gs = GridSpec(2, 2,hspace=0.00,wspace=0.1,width_ratios=[25,1])
  ax1 = pl.subplot(gs[0,0])
  im=ax1.imshow(xv.T, origin='lower', cmap=matplotlib.cm.jet,extent=(0,100,0,1.0),aspect='auto')  
  xax1=ax1.get_xaxis()
  xax1.set_ticks([])
  ax3 = pl.subplot(gs[0,1])
  #cbar=pl.colorbar(im,cax=ax3,shrink=0.5)
  cbar=pl.colorbar(im,cax=ax3)
  ax2 = pl.subplot(gs[1,0])
  ax2.plot(np.sin(x))
  pl.savefig('test.pdf')
  </code></pre>
  
  <p>I would like to keep the two plots sharing the same x-axis but I would like to 
  shrink the colorbar as well. If I use the commented line it does not work. What is the
  better, most elegant, way to do that? I think I should use <code>make_axes_locatable</code> at some point, but I do not know how to use it in the proper way without changing the imshow
  x-axis length. </p>
  
  <p>Thank you.</p>