title: Scala folding tuples
body: <pre><code>Map(Mary -&gt; List(("Mary", 7065), ("Mary", 2604), ("Mary", 1414))):
    Map[String, List[(String, Int)]]
  </code></pre>
  
  <p>How can I fold the maps to produce something like</p>
  
  <pre><code>Map("Mary" -&gt; List(("Mary", 7065+2604+1414))):
    Map[String, List[(String, Int)]]
  </code></pre>
  
  <p>?</p>