CentOS 7 now uses SystemD instead of SysV

Ensure centos 7 is capable of using systemd for checking if the service is running/restarting
Merge pull request #428 from jeteokeeffe/patch-1

CentOS 7 now uses SystemD instead of SysV
Only install EPEL if not already installed.

Refs #422. Closes #421.

Enable the systemd service. Closes #425.
Update changes log
If system is using systemd, enable services.

Closes #425.