I want to add to this even though it's a bit old.
the "sign_out" link didn't work, despite having :method => :delete.
The comment indicating that <%= javascript_include_tag :defaults %>
must be included reminded me I had recently added JQuery java script and used simple <script src=""/>
tags to include them.
When I moved them from after the :defaults to before, the sign_out started working again.
Hopefully this helps someone.