Making it an .rb file makes babushka load it, reopen stdout and stderr into a logfile, silencing itself on the terminal, and then running a backup (which raises because it can't sudo as postgres). This reverts commit 37f4373.
Rubies since 2.1 don't include the patchlevel in their version name.
Using extconf requires an existing ruby & mkmf of a particular version (e.g. 1.8/1.9 mkmf can't configure a 2.1 build). Instead, just make sure the extensions we want were included on their own.
I don't think this is strictly necessary, but it's nice to be explicit about it.