title: Pandas skipping x tick labels
body: <p>I have a plot with 15 axis labels and Pandas automatically defaults to showing every other category name.  How do I get it to show ALL of the x-axis labels without skipping items?</p>
  
  <pre><code>rows = []
  for x in range(0,14):
      rows.append(['a',14-x])
  
  df = pd.DataFrame(rows)
  df = df.set_index(0)
  df.plot(xticks=df.index)
  </code></pre>