Added new security question to sign up, Added notification for unconfirmed emails

• Added:
- new security question to sign up
- notification for unconfirmed emails
- modal for describing issue with Gab emails

app/views/auth/registrations/new.html.haml

@@ -34,6 +34,9 @@
 
   = f.input :invite_code, as: :hidden
 
+  .fields-group
+    = f.input :challenge, wrapper: :with_label, label: "Are you human? What is #{@challenge_add_1} + #{@challenge_add_2} = ", required: true, input_html: { 'aria-label' => "Are you human? What is #{@challenge_add_1} + #{@challenge_add_2}", :autocomplete => 'off' }
+
   .fields-group-agreement
     = f.input :agreement, as: :boolean, wrapper: :with_label, label: t('auth.checkbox_agreement_html', about_tos_path: about_tos_path)