Prevent csrf attacks on login

Change-Id: I9e6225f80136899e1ab90eac58d8206d2f7b1819
diff --git a/templates/layouts/main.html.ep b/templates/layouts/main.html.ep
index 83b637d..78ed722 100644
--- a/templates/layouts/main.html.ep
+++ b/templates/layouts/main.html.ep
@@ -33,6 +33,7 @@
 <fieldset>
   %= form_for 'login', class => 'login', begin
   <legend><span><%= loc 'login' %></span></legend>
+    %= csrf_field
     %= text_field 'handle_or_email', placeholder => loc('userormail')
     <div>
       %= password_field 'pwd', placeholder => loc('pwd')