title: MongoMapper Disable Embedded ID
body: <p>Is it possible to disable _id for embedded documents?</p>
  
  <p>For example if have a parent with an embedded child document. it seems kind of pointless for the child to have an id if i don't intend to reference the child from anywhere else.</p>
  
  <pre><code>class Parent
    include MongoMapper::Document
    one :child
    key :name
  end
  
  class Child
    include MongoMapper::EmbeddedDocument
    key :name
  end
  
  parent = Parent.new(:name =&gt; 'parent',
    :child =&gt; Child.new(:name =&gt; 'child'))
  
  puts parent.to_json
  
  {"id":"4ebeddde51d9e56dcb000006","name":"parent",
  "child":{
      "id":"4ebeddde51d9e56dcb000005",
      "name":"child"}}
  </code></pre>