title: Has Many Through relationship with accepts nested attributes
body: <p>I understand that in order to use nested attributes I need to use a  has many through relationship instead of a has and belong to many so I have the following set up:</p>
  
  <pre><code>class Deed &lt; ActiveRecord::Base
      has_many :deeds_title_abstracts
      has_many :title_abstracts, through: :deeds_title_abstracts
  end
  
  class TitleAbstract &lt; ActiveRecord::Base
      has_many :deeds_title_abstracts
      has_many :deeds, through: :deeds_title_abstracts
      accepts_nested_attributes_for :deeds
  end
  
  class DeedsTitleAbstracts &lt; ActiveRecord::Base
    belongs_to :deeds
    belongs_to :title_abstracts
  end
  </code></pre>
  
  <p>In my Controller for Title Abstracts I have</p>
  
  <pre><code>def new
     @title_abstract = TitleAbstract.new(params[:title_abstract])
     @title_abstract.deeds.build
     respond_with(@title_abstract)
  end
  </code></pre>
  
  <p>I am using cocoon in the view but I don't think that is the problem since I get this error: </p>
  
  <pre><code>  uninitialized constant TitleAbstract::DeedsTitleAbstract
  </code></pre>
  
  <p>I get the following when I look at it through the Console</p>
  
  <pre><code>   @title_abstract =TitleAbstract.new(params[:title_abstract])
     =&gt; #&lt;TitleAbstract id: nil, name: nil, due_date: nil, comments: nil,     created_at: nil, updated_at: nil&gt;
     &gt;&gt; @title_abstract.deeds.build
     !! #&lt;NameError: uninitialized constant TitleAbstract::DeedsTitleAbstract&gt;
  </code></pre>
  
  <p>I think there is something wrong with my Has Many Through models</p>