Adding RVM support to the rails_test subsuite.

Related to #4. #OSL
Removing RBENV-specific codes. Sigh.

Related to #4. #OSL
Updating old, old dev dependencies, and making sure we resolve "unindent"
Updating old, old gemspec.

For the record, this is why I hate including gemspecs in the git repo.
Nokogiri 1.6 doesn't support old versions of ruby that are required for old versions of rails.
Adding test coverage for Rails 4.

Related to #4. #OSL
Adding support for Rails 4.

Resolves #4.