title: Create Weak Multimap with Google Collections
body: <p>Is there an equivalent to the nice MapMaker for MultiMaps? 
  currently i create the cache like this:</p>
  
  <pre><code>    public static Map&lt;Session,List&lt;Person&gt;&gt; personCache = new MapMaker().weakKeys().makeMap();
  </code></pre>
  
  <p>the whole point of MultiMap is to avoid the nested List Values. is there any way to construct the multimap with weak keys?</p>