title: Joining same-key dictionaries into a dataframe in pandas
body: <p>How to create a pandas <code>DataFrame</code> out of two and more dictionaries having common keys? That is, to convert</p>
  
  <pre><code>d1 = {'a': 1}
  d2 = {'a': 3}
  ...
  </code></pre>
  
  <p>into a dataframe with columns <code>['d1', 'd2', ...]</code>, rows indexed like <code>"a"</code> and values determined by the respective dictionaries?</p>