switching to sub-man for enable calls

yum-utils is occasionally unreliable when modifying Red Hat repositories

This change switches to the more reliable subscription-manager
repository modification routine and combines it into one command for a
bit better performance.
Merge pull request #94 from mccun934/20141119-1123

switching to sub-man for repo enable calls
Enable must be specified per REPOID for subscription-manager enable.
Merge pull request #95 from ehelms/fix-sub-man-enable

Enable must be specified per REPOID for subscription-manager enable.