Enh: add gpg verification during build
Enh: add RHEL6 signing key as well, it's useful for source rebuilds.
Fix: maintainer name
Make things a bit more logical: update before installing, and perform install in single step
Cleanup yum.conf, better default options, remove unused repos.
Enh: remember to clean metadata, just in case; don't use unnecessary -y switch, already configured in yum.conf