Add spec tests for Puppet face component, mainly around error checking.
Due to the use of `puppet module list`, the behavior of the `modules`
and `server` actions are not very feasible to test via spec testing.
Additionally, make a few minor changes to the gem file, and make a
small change in `check_required_features` to reflect the fact that
this module will no longer support anything earlier than Ruby 1.9.
Hailee Kenney