Use EL instead of RHEL

To be more inclusive of variants like CentOS
Fixed read-database parameters in class puppetdb
Merge pull request #134 from tdevelioglu/master

Fixed read-database parameters in class puppetdb
Merge pull request #133 from ghoneycutt/patch-1

Use EL instead of RHEL
do not manage firewall for postgres, puppetlabs/postgres module from
git has dropped that silly firewall management support.