title: Select on hash with indifferent access not working
body: <p>I am trying to deal with inconsistent keys (Strings/Symbols) in hashes. I thought that HashWithIndifferentAccess would be the answer but I am getting some slightly confusing results when trying to do some basic operations on these hashes</p>
  
  <p>For example I have the following HashWithIndifferentAccess</p>
  
  <pre><code>(rdb:1) metadata
  {"indexes"=&gt;["respondent", "brand"], "columns"=&gt;["rating"], 
   "value_labels"=&gt;{}, "column_labels"=&gt;{}}
  (rdb:1) metadata.class
  ActiveSupport::HashWithIndifferentAccess
  </code></pre>
  
  <p>when I try the following select I get an empty hash</p>
  
  <pre><code>(rdb:1) metadata.select{ |k, v| [:indexes, :columns, :value_labels, :column_labels]
  .include? k }
   {}
  </code></pre>
  
  <p>Are all common hash operations available with HashWithIndifferentAccess ? Why is this operation returning an empty hash</p>