app/views/layouts/_navigation_links.html.erb
<%# add navigation links to this file %>
<% if user_signed_in? %>
<li><%= link_to 'Edit account', edit_user_registration_path %></li>
<li><%= link_to 'Sign out', destroy_user_session_path, :method=>'delete' %></li>
<% else %>
<li><%= link_to 'Sign in', new_user_session_path %></li>
<li><%= link_to 'Sign up', new_user_registration_path %></li>
<% end %>