Track all modifications to a PostgreSQL table

We have a table which has only roughly 500 rows, but it is very important for us. I want see all changes which happen to this table. The changes should get tracked with a timestamp. I don't want the tracking to happen in the application code, since I want to track changes which happen via psql shell, too. I am happy with a PostgreSQL specific solution, since I don't use a different DB in this context.