* Update devise to latest version

* use letter_opener for mails in development
* bring back the flash
* fix redirect loop for logging in
* move all mailer/devise settings to config/config.yml

config/initializers/devise.rb

@@ -1,10 +1,12 @@
 # Use this hook to configure devise mailer, warden hooks and so forth.
 # Many of these configuration options can be set straight in your model.
 Devise.setup do |config|
+  # ==> Secret key
+  config.secret_key = CONFIG['devise_secret_key'] 
   # ==> Mailer Configuration
   # Configure the e-mail address which will be shown in Devise::Mailer,
   # note that it will be overwritten if you use your own mailer class with default "from" parameter.
-  config.mailer_sender = "no-reply@conference.opensuse.org"
+  config.mailer_sender = CONFIG['devise_mail_sender']
 
   # Configure the class responsible to send e-mails.
   # config.mailer = "Devise::Mailer"

config/initializers/osem.rb

@@ -1 +0,0 @@
-OSEM_CONFIG = YAML.load_file("#{Rails.root}/config/config.yml")[Rails.env]