enable the EPEL YUM repo on CentOS
enable the EPEL YUM repo on CentOS

This allows us to install libyaml-devel and 
properly compile Ruby 1.9.3.
szechyjs/omnibus,pskrz/omnibus,pskrz/omnibus,mattray/omnibus,hugosato/omnibus,ashhher3/omnibus,hugosato/omnibus,sh9189/omnibus,servebox/omnibus,rapid7/omnibus,lvfeng1130/omnibus,adamleff/omnibus,servebox/omnibus,Altiscale/omnibus,chef/omnibus,rhass/omnibus,strangelittlemonkey/omnibus,Altiscale/omnibus,Altiscale/omnibus,jamesn/omnibus,jamesn/omnibus,Scalr/omnibus,pskrz/omnibus,strangelittlemonkey/omnibus,rhass/omnibus,mattray/omnibus,rhass/omnibus,servebox/omnibus,DataDog/omnibus-ruby,lvfeng1130/omnibus,3ofcoins/chef-omnibus,adamleff/omnibus,chef/omnibus,jamesn/omnibus,rapid7/omnibus,3ofcoins/chef-omnibus,adamleff/omnibus,ashhher3/omnibus,mattray/omnibus,strangelittlemonkey/omnibus,sh9189/omnibus,higanworks/omnibus,chef/omnibus,sh9189/omnibus,intfrr/omnibus,ashhher3/omnibus,lvfeng1130/omnibus,higanworks/omnibus,DataDog/omnibus-ruby,intfrr/omnibus,3ofcoins/chef-omnibus,Scalr/omnibus,intfrr/omnibus,Scalr/omnibus,szechyjs/omnibus,DataDog/omnibus-ruby,hugosato/omnibus,rapid7/omnibus,szechyjs/omnibus,higanworks/omnibus