views/default.erb
<!DOCTYPE html>
<html lang='en'>
<%= erb :'includes/header' %>
<body>
<%= erb :'includes/github-corner' if @github_url %>
<div class='container'>
<div class='row'>
<div class='col-md-1'></div>
<div class='col-md-10'>
<%= yield %>
</div>
<div class='col-md-1'></div>
</div>
</div>
<%= erb :'includes/footer' %>
</body>
</html>