title: Convert pandas series of lists to dataframe
body: <p>I have a series made of lists</p>
  
  <pre><code>import pandas as pd
  s = pd.Series([[1, 2, 3], [4, 5, 6]])
  </code></pre>
  
  <p>and I want a DataFrame with each column a list. </p>
  
  <p>None of <code>from_items</code>, <code>from_records</code>, <code>DataFrame</code> <code>Series.to_frame</code> seem to work. </p>
  
  <p>How to do this?</p>