(maint) Add support for running specs

This brings over from the puppet repo bits that allow specs
to work, including:
* spec/fixtures/unit/provider/naginator
* spec/lib/puppet_psec
* spec/spec_helper.rb
* Gemfile

Gemfile was stripped down, but puppet_spec was not so there
is a bunch of stuff in there that is probably not needed.
I.e. more cleanup needed.
Merge pull request #1 from kylog/make-specs-work

(maint) Add support for running specs