Fix sign out link

The correct HTML attribute to send a DELETE request would be
`data-turbo-method`, but then it still fails with JS turned off, which
is unnecessary.

fixes #61

config/initializers/devise.rb

@@ -291,7 +291,7 @@ Devise.setup do |config|
   # config.navigational_formats = ['*/*', :html]
 
   # The default HTTP method used to sign out a resource. Default is :delete.
-  config.sign_out_via = :delete
+  config.sign_out_via = :get
 
   # ==> OmniAuth
   # Add a new OmniAuth provider. Check the wiki for more information on setting