title: Plotting pandas dataframe with years
body: <pre><code>       error   Months    Year
  0  15.198688      Jan  2011.0
  1  13.793969  Jan_Feb  2011.0
  2  15.171848  Jan_Mar  2011.0
  3   5.779007  Jan_Apr  2011.0
  4   1.615044  Jan_May  2011.0
  5   1.536096  Jan_Jun  2011.0
  6   1.159742  Jan_Jul  2011.0
  0   1.697396      Jan  2012.0
  1   5.149847  Jan_Feb  2012.0
  2   0.876639  Jan_Mar  2012.0
  3   1.865001  Jan_Apr  2012.0
  4   0.333077  Jan_May  2012.0
  5   2.056728  Jan_Jun  2012.0
  0   9.676028      Jan  2013.0
  1   3.919200  Jan_Feb  2013.0
  2   4.171534  Jan_Mar  2013.0
  3   2.318090  Jan_Apr  2013.0
  4   0.786901  Jan_May  2013.0
  5   0.936041  Jan_Jun  2013.0
  6   0.115029  Jan_Jul  2013.0
  </code></pre>
  
  <p>Is there a way to plot the pandas dataframe above so that plot has 3 lines (one for each of the 3 unique years). Y-axis has 'error' column and X-axis shows the Month. The legend should be the 3 years: 2011, 2012, 2013</p>
  
  <p>For X-axis, if month is 'Jan_Feb', then label should just say 'Feb'. if month is 'Jan', then label should say 'Jan'</p>
  
  <p>I tried df.plot(), but it plots everything in one plot</p>