title: Convert nested dictionary list to multi column dataframe
body: <p>I have a nested dictionary list that looks like this.</p>
  <pre><code>{'a': [{'aa': '10', 'bb': '11'}, {'aa': '12', 'bb': '13'}], 'b': [{'aa': '14', 'bb': '15'}, {'aa': '16', 'bb': '17'}]}
  </code></pre>
  <p>and I would like to convert the dictionary list above to a multi column dataframe, preferably like this.</p>
  <p>**The dictionary might not be the same length</p>
  <pre><code>a       b   
  aa  bb  aa  bb
  10  11  14  15
  12  13  16  17
  </code></pre>
  <p>any help is appreciated.</p>