Add Rescue From as a rails til

rails/rescue-from.md

@@ -0,0 +1,21 @@
+# Rescue From
+
+The
+[`rescue_from`](http://api.rubyonrails.org/classes/ActiveSupport/Rescuable/ClassMethods.html)
+method, provided by `ActiveSupport`, is a handy way to provide a catch-all
+response to a particular exception.
+
+For instance, if many of the controllers in your application raise a
+`User::NotAuthorized` error for unauthorized requests, the
+`ApplicationController` can provide a unified response. This will help dry
+up your controllers and prevent any potential inconsistencies.
+
+```ruby
+class ApplicationController < ActionController::Base
+  rescue_from User::NotAuthorized do |exception|
+    # respond with some Not Authorized page
+  end
+
+  ...
+end
+```