add centos support
Fix mongo setup for RHEL system

* Calling oo-mongo-setup directly in Puppet will not work
  because it is invoking the wrong ruby.
* ruby-devel dependency in init.pp should be coming from
  ruby193 SCL on RHEL; resolve rubygems in a similar fashion
  as well
Merge pull request #53 from worldline/centos

Add centos support
Merge pull request #57 from dvusboy/mongo_fixes

Fix mongo setup for RHEL system
Adding missing repository dependencies to scl package definitions