title: Records in join table destroyed automatically in HABTM association?
body: <p>Let's say I have an association where User has and belongs to many Roles.  When I destroy the user, is the record in the join table automatically removed as well?  Or do I need to use :dependent => :destroy?  What about if I destroy a Role?</p>
  
  <pre><code>class User &lt; ActiveRecord::Base
     has_and_belong_to_many :roles # need to use :dependent =&gt; :destroy to remove join record?
  end
  
  class Role &lt; ActiveRecord::Base
     has_and_belong_to_many :users # need to use :dependent =&gt; :destroy to remove join record?
  end
  </code></pre>