Require rubygems

According to the puppetlabs_spec_helper documentation:

https://github.com/puppetlabs/puppetlabs_spec_helper#usage

this is how it's done.
Merge branch '3402_tests' into 3404_test_coverage
Implement basic tests for cs_primitive provider
Implement basic tests for cs_property provider
Merge remote-tracking branch 'upstream/master' into 3404_test_coverage
Revert "Merge branch '3402_tests' into 3404_test_coverage"

This reverts commit 86e17952768bb7c052cae68c5b94ecf28c251d9f, reversing
changes made to 33b46ee789760c6a3f8b262e86168b7d57003881.

We don't want this, because I guess requiring rubygems in Rakefile is an
anti-pattern, or something. Upstream now has a Gemfile, which solves the
issue of making the gems available in a better way.
Merge pull request #43 from bitglue/3404_test_coverage

write some tests