bump to v9.2.4, closes boxen/puppet-postgresql#9

As per request for most recent version, as @wfarr says, "Should be as
simple as a version bump + sha fix."

This module still really needs tests, but someone who cares more about
postgres than me will have to take care of that.
Merge pull request #14 from mroth/v9.2.4

bump to v9.2.4, closes boxen/puppet-postgresql#9