title: How to identify missing days from a list of start and end dates?
body: <p>How to identify missing dates from a list of <code>(start_date, end_date)</code> tuples? </p>
  
  <p>For example, how to identify missing dates in the below list:</p>
  
  <pre><code>dates = [('2011-01-01', '2011-01-14'), ('2011-01-15','2011-01-31'), 
           ('2011-02-01', '2011-02-14'), ('2011-03-01', '2011-03-14'), 
           ('2011-03-16', '2011-03-31')]
  </code></pre>
  
  <p>The above example has the following missing dates:</p>
  
  <ul>
  <li><code>2011-02-15</code> to <code>2011-02-28</code></li>
  <li><code>2011-03-15</code></li>
  </ul>
  
  <p>How do identify all missing days from a list of start and end date tuples?</p>