Fix specs with Ruby 2.0, clean up use of deprecated RSpec features.

Spec fix for Ruby 2.0 (fixing require paths in spec_helper.rb) comes from upstream at https://github.com/heroku/databasedotcom/commit/f402a0d57d6d3223e2fff5f1ebd96a8842ec804c.

Cleanup of deprecated RSpec features from me, because it was hard to tell if the specs were actually running fine or not with all the deprecation noise.