maint: just require 'spec_helper', thanks rspec2
rspec2 automatically sets a bunch of load-path stuff we were by hand, so we
can just stop. As a side-effect we can now avoid a whole pile of stupid things
to try and include the spec_helper.rb file...
...and then we can stop protecting spec_helper from evaluating twice, since we
now require it with a consistent name. Yay.
Reviewed-By: Pieter van de Bruggen <pieter@puppetlabs.com>