app/views/layouts/application.html.erb
<!DOCTYPE html>
<html>
<head>
<title>Blog</title>
<%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true %>
<%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>
<%= csrf_meta_tags %>
</head>
<body>
<% if flash[:notice] %>
<p>
<%= flash[:notice] %>
</p>
<% end %>
<% if flash[:alert] %>
<p>
<%= flash[:alert] %>
</p>
<% end %>
<% if logged_in? %>
<%= link_to 'Sign Out', logout_path %>
<% else %>
<%= link_to 'Sign In', login_path %>
<% end %>
<hr>
<%= yield %>
</body>
</html>