app/views/layouts/application.html.erb
<!DOCTYPE html>
<html lang="en">
<%= render 'layouts/head' %>
<body>
<%= render 'layouts/navbar' %>
<div class='container'>
<div id="<%= content_wrapper_id %>">
<%= render partial: 'layouts/flash', locals: {flash: flash} %>
<%# Main Content %>
<% if show_title? %>
<div class="page-header">
<h1 id="page_title">
<%= yield(:title) %>
<small id="subtitle"><%= yield(:subtitle) %></small>
</h1>
</div>
<% end %>
<div class="row">
<% if content_for?(:left_nav) %>
<div class="col-md-2">
<%= render 'layouts/left_nav' %>
</div>
<% end %>
<div class="<%= content_for?(:left_nav) ? "col-md-10" : "col-md-12" %>">
<%= yield %>
</div>
</div>
<%= render 'layouts/footer' %>
<%= render 'layouts/modal' %>
</div>
</div>
</body>
</html>