Merge pull request #58 from mckern/use_epel

(maint) Update RHEL7 mock stub to pull Puppet from EPEL
Merge pull request #59 from mckern/use_epel

(maint) Add Puppet Labs modules to RHEL7 mock stub
Merge pull request #60 from mckern/use_epel

(maint) Add rubygem-rgen to EPEL whitelist for RHEL7
Merge pull request #61 from mckern/use_epel

(maint) Add redhat-release-everything to RHEL7 mock setup list
(maint) Reconcile changes from FOSS RHEL7 mockstub with PE RHEL7 mockstub

This will ensure we're using a consistently usable base when we try to
build RHEL7 PE packages.