cosmetic updates to fixtures.yml
removed existing files under spec/fixtures/modules

Using puppetlabs_spec_helper and .fixtures.yml means these files can be
automatically installed at test time rather than manually.
removed rspec-puppet plumbing

puppetlabs_spec_helper manages paths under spec/fixtures and finding
spec files, so that logic can be removed from Rakefile and spec_helper
updates to Gemfile.lock

Some of the modules under Gemfile.lock were pretty old and spamming test
output with deprecation warnings. Updated to use latest modules for
testing.