Postgresql: replica and HA

I've postgresql 9.4.

I'm aware that there are many answer on DBA and SO, I'm aware of the wiki and the documentation.

But anyway, I can't understand in a simple way what's the right way to have a master postgresql server, and a slave postgresql server that is updated from the master (as soon as possible, to reduce data loss).

Also I would need a way to do automatic promotion of the slave to master in case of failing master.

Should I use Repmgr? Or I should just use Postgresql's functions?

Thanks