Added check for SELinux running in enabled/permissive

In order for SELinux to properly limit the access for gears within
OpenShift SELinux must have access controls over the system.  This
check ensures that systems are at the very least running OpenShift
in permissive mode if not enabled.
Merge pull request #51 from brianredbeard/selinux_require

Added check for SELinux running in enabled/permissive