title: Convert dictionary in pandas' column to dictionary value
body: <p>I have a pandas' DataFrame that has a dictionary as the value in one of the columns e.g.</p>
  
  <pre><code>    A    B
  1   x   {u'count': 3}
  2   y   {u'count': 2}
  </code></pre>
  
  <p>Is there a way to convert the elements in the B column to just the dictionary value in a single operation other than iterating through the entire DataFrame?</p>
  
  <p>So the Dataframe would appear like:</p>
  
  <pre><code>     A    B
  1    x    3
  2    y    2
  </code></pre>