refs #813 - LDAP group support changes

Follows https://github.com/theforeman/foreman/pull/529 and replaces #262.

Will tag the gem after.  The version will also be bumped whenever it's released. (done)

Green scratch builds:
http://koji.katello.org/koji/taskinfo?taskID=134711
http://koji.katello.org/koji/taskinfo?taskID=134713
http://koji.katello.org/koji/taskinfo?taskID=134715
It's a weird process thing, but I'll run `tito tag --keep-version` after this gets pushed which will generate a changelog entry as an additional commit.