Change Title with the application name. (#34)

Change Title in the head with the global application name.

app/views/shared/_head.html.erb

@@ -1,4 +1,4 @@
-<title>Jumpstart</title>
+<title><%= Rails.configuration.application_name %></title>
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">