Add user model through devise. Add some basic layout. Start testing in travis.

app/views/users/mailer/confirmation_instructions.html.erb

@@ -0,0 +1,5 @@
+<p>Welcome <%= @email %>!</p>
+
+<p>You can confirm your account email through the link below:</p>
+
+<p><%= link_to 'Confirm my account', confirmation_url(@resource, confirmation_token: @token) %></p>