title: replace numbers on X axis with dates when using line plot in matplotlib
body: <p>I am plotting a straight line plot with an array of numbers</p>
  
  <pre><code>fig, ax = plt.subplots()
  ax.plot(x, 0 * x)
  </code></pre>
  
  <p>x is the  array:</p>
  
  <pre><code>array([  0,1,2,3,4,5,6,7,8,9,10 ])
  </code></pre>
  
  <p>The line is fine but I want to display dates on the x axis.. I want to associate
  a date with each of the number and use those as my x ticks.</p>
  
  <p>Can anyone suggest something?</p>