title: Matplotlib / Pandas histogram incorrect alignment
body: <pre>
  # A histogram
  n = np.random.randn(100000)
  fig, axes = plt.subplots(1, 2, figsize=(12,4))
  
  axes[0].hist(n)
  axes[0].set_title("Default histogram")
  axes[0].set_xlim((min(n), max(n)))
  
  axes[1].hist(n, cumulative=True, bins=50)
  axes[1].set_title("Cumulative detailed histogram")
  axes[1].set_xlim((min(n), max(n)));
  </pre>
  
  <p><img src="https://i.stack.imgur.com/kqhCI.png" alt="ipython notebook histogram"></p>
  
  <p>This is from an ipython notebook <a href="http://nbviewer.ipython.org/github/jrjohansson/scientific-python-lectures/blob/master/Lecture-4-Matplotlib.ipynb" rel="nofollow noreferrer">here</a> <code>In[41]</code></p>
  
  <p>It seems that the histogram bars don't correctly align with the grids (see first subplot). That is the same problem I face in my own plots.</p>
  
  <p>Can someone explain why?</p>