First of all: BE WARNED!
These settings are not recommended for all of you (if any) in production as they might cause you data corruption or loss in case of sudden hardware failure.
I would on suggest to have these settings used in a development environment, where you have to run many tests for your application which include database side create/drop transactions.
My case here was that I ran so much database inclusive tests, that I got fed up with PostgreSQL's ~6s database creation time. So I just Googled it a few days how this could be done in a dev env. So here it is, you just set these two variables in your postgresql.conf file and reastart the database.