adding devise config to respond with json

config/initializers/devise.rb

@@ -267,4 +267,11 @@ Devise.setup do |config|
   # When using OmniAuth, Devise cannot automatically set OmniAuth path,
   # so you need to do it manually. For the users scope, it would be:
   # config.omniauth_path_prefix = '/my_engine/users/auth'
+
+
+  # If using rails-api, you may want to tell devise to not use ActionDispatch::Flash
+  # middleware b/c rails-api does not include it.
+  # See: http://stackoverflow.com/q/19600905/806956
+  config.navigational_formats = [:json]
+
 end