rspec-system 2 helpers

Convert all helpers to use the rspec-system 2 helper format. This provides
the 'helper as a subject' syntactical sugar.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #9 from kbarber/rspec-system-2

rspec-system 2 helpers
Release 2.0.0

Signed-off-by: Ken Barber <ken@bob.sh>
Remove coupling with Bundler

Bundler is not required to use this library and explicitly requiring and
calling `Bundle.setup` or `Bundle.require` is discouraged. This commit
removes much of the code that tightly couples rspec-system-puppet with
bundler and updates the documentation to reflect this.
Merge pull request #10 from hunner/bundle_exec

Remove coupling with Bundler