add -- to su so arguments are correctly parsed

Without this, the --local option intended for gem list is instead
applied to su, which results in a silent failure. Since the su returns
non-zero, Puppet interprets this as needing to run rbenv::gem, which
gets run during every Puppet apply regardless of whether the gem is
already in place or not.
added puppetlabs_spec_helper to Gemfile
added puppetlabs_spec_helper/rake_tasks to Rakefile
added .fixtures.yml, puts vcsrepo into place for testing
updated tests for vcsrepo

Tests on git execs are now testing the vcsrepo declarations. The test
covering plugin updates has been removed since ensure => latest on
vcsrepo should cover that.

Also fixed some errors caught by testing... yay tests!
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.
add -- to su so arguments are correctly parsed

Without this, the --local option intended for gem list is instead
applied to su, which results in a silent failure. Since the su returns
non-zero, Puppet interprets this as needing to run rbenv::gem, which
gets run during every Puppet apply regardless of whether the gem is
already in place or not.
Merge branch 'gem_install_always_runs'
Merge branch 'vcsrepo_for_plugins'