title: Deserialzing works in gson-2.1 but not gson-2.4.4
body: <p>I have this snippet: </p>
  
  <pre><code>HashMap&lt;String, List&lt;ClassOne&gt;&gt; mappingMap = new HashMap&lt;String, List&lt;ClassOne&gt;&gt;();
  String key = "pop";
  ClassOne c1 = new ClassOne();
  c1.setCategoryName("categoryName");
  ArrayList&lt;ClassOne&gt; al = new ArrayList&lt;ClassOne&gt;();
  al.add(c1);
  mappingMap.put(key, al);
  Gson gson = new Gson();
  String data = gson.toJson(mappingMap);
  HashMap&lt;String, List&lt;ClassOne&gt;&gt; dmm = gson.fromJson(data, new TypeToken&lt;Map&lt;String, List&lt;ClassOne&gt;&gt;&gt;() {}.getType());
  </code></pre>
  
  <p>It when run with the gson-2.1.jar , it works fine. When run with the gson-2.2.4.jar I get the following exception</p>
  
  <blockquote>
    <p>java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap
    cannot be cast to java.util.HashMap   at com......</p>
  </blockquote>
  
  <p>Wondering if anyone could explain, or point out what I am doing incorrectly. </p>