<!DOCTYPE html>
<html>
<head>
  <title>BlogSample</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 user_signed_in? %>
	Hello, <%= current_user.username %> | <%= link_to 'Sign Out', destroy_user_session_path, method: :delete %>
<% else %>
	<%= link_to 'Sign In', new_user_session_path %>
<% end %>

<p class="notice"><%= notice %></p>
<p class="alert"><%= alert %></p>

<%= yield %>

</body>
</html>

<!DOCTYPE html>
<html>
<head>
  <title>BlogSample</title>
  <%= stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track' => true %>
  <%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>
  <%= csrf_meta_tags %>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <script data-require="bootstrap@*" data-semver="3.3.6" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
  <link data-require="bootstrap-css@3.3.6" data-semver="3.3.6" rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.css" />
  <script data-require="jquery@*" data-semver="2.2.0" src="https://ajax.googleapis.com/ajax/libs/jquery/2.2.0/jquery.min.js"></script>
</head>
<body>

<% if user_signed_in? %>
	Hello, <%= current_user.username %> | <%= link_to 'Sign Out', destroy_user_session_path, method: :delete %>
<% else %>
	<%= link_to 'Sign In', new_user_session_path %>
<% end %>

<p class="notice"><%= notice %></p>
<p class="alert"><%= alert %></p>

<%= yield %>

</body>
</html>

Add Bootstrap CDN and jQuery
Add Bootstrap CDN and jQuery
