title: python intersect of dict items
body: <p>Suppose I have a dict like:</p>
  <pre><code>aDict[1] = '3,4,5,6,7,8'
  aDict[5] = '5,6,7,8,9,10,11,12'
  aDict[n] = '5,6,77,88'
  </code></pre>
  <p>The keys are arbitrary, and there could be any number of them. I want to consider every value in the dictionary.</p>
  <p>I want to treat each string as comma-separated values, and find the intersection across the entire dictionary (the elements common to all dict values). So in this case the answer would be '5,6'. How can I do this?</p>