title: python pandas flatten a dataframe to a list
body: <p>I have a df like so:</p>
  
  <pre><code>import pandas
  a=[['1/2/2014', 'a', '6', 'z1'], 
     ['1/2/2014', 'a', '3', 'z1'], 
     ['1/3/2014', 'c', '1', 'x3'],
     ]
  df = pandas.DataFrame.from_records(a[1:],columns=a[0])
  </code></pre>
  
  <p>I want to flatten the df so it is one continuous list like so:</p>
  
  <p><code>['1/2/2014', 'a', '6', 'z1', '1/2/2014', 'a', '3', 'z1','1/3/2014', 'c', '1', 'x3']</code></p>
  
  <p>I can loop through the rows and <code>extend</code> to a list, but is a much easier way to do it?</p>