[WIP] Spec overhaul.

This is a work in progress PR to modernize some of the tests inside stdlib and free it from the shackles of old rspec.

I rewrote some of the function tests to use the puppet_spec helpers from puppet's core, but in many cases only minimal changes were made to make sure the tests pass.  One test, anchor, still fails as it tries to apply a real catalog on my machine and I don't have an /etc/puppet/, but the rest should hopefully scrape through travis.