Added "devise" for authentication.

app/views/layouts/_user_widget.slim

@@ -0,0 +1,6 @@
+- if user_signed_in?
+  p Welcome #{current_user.email}
+  = link_to 'Logged In [click to logout]', destroy_user_session_path, :method => :delete
+- else
+  p You are not signed in.
+  = link_to 'Login', new_user_session_path

app/views/layouts/application.html.slim

@@ -16,6 +16,7 @@ html
     // TODO: move topbar somewhere else than packages
     = render 'layouts/topbar'
     #messages
+    = render 'layouts/user_widget'
     = render 'layouts/messages'
     #content
       = yield