app/views/layouts/application.html.erb
<!DOCTYPE html>
<html>
<head>
<title>WatchIoT</title>
<%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true %>
<%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>
<%= csrf_meta_tags %>
</head>
<body>
<%= render 'layouts/nav_app' %>
<%= yield %>
<%= render 'layouts/footer_app' %>
<script>
$('.img-circle').each(function(index, element){
var email = $(element).data("email");
$(element).attr("src", Gravtastic(email, {default: 'identicon'}));
})
</script>
</body>
</html>