update to RSpec 3.1 in dev
set RSpec to at least 2.99.0 in gemspec
really fix superclass mismatch (#222)
fix specs for RSpec 3.1
add rubocop and guard-rubocop config (dev)
fix Rubocop offenses
add gemfile for RSpec 2.99
add test:all_versions Rake task
update CONTRIBUTING.md
Merge pull request #289 from guard/update_dev_tools

Update dev tools