FEATURE: refresh session cookie at most once an hour

This feature ensures session cookie lifespan is extended
when user is online.

Also decreases session timeout from 90 to 60 days.
Ensures all users (including logged on ones) get expiring sessions.

db/migrate/20160725015749_rename_auth_token_created_at.rb

@@ -0,0 +1,5 @@
+class RenameAuthTokenCreatedAt < ActiveRecord::Migration
+  def change
+    rename_column :users, :auth_token_created_at, :auth_token_updated_at
+  end
+end