title: Pandas Dataframe: get a multiindex row above the current column headings and merge the cells into a single cell
body: <p>I want to use pandas dataframe to add a a row above the current column heading. The first row should be a singly-merged cell that contains today's date.</p>
  
  <p>My current dataframe looks like below</p>
  
  <pre><code>index   name   field1    field2
    1     John    blah      blah
    2     Dave    blah      blah
    .........
  </code></pre>
  
  <p>But I'm trying to make the dataframe to look like this:</p>
  
  <pre><code> T  O  D  A  Y \' s   D  A  T  E 
  index   name   field1    field2
    1     John    blah      blah
    2     Dave    blah      blah
    .........
  </code></pre>
  
  <p>I hear you can use <code>pd.multiindex.</code>..but can't seem to get a grip of this. Can anyone help?</p>