Add dependencies to make tests pass
Improve CI

- Rubygems over HTTPS
- Test against ree, 1.8.7, and jruby-20mode
- Match test sequel versions to gemspec
Bump rspec, fix deprecations, use expect syntax
Simplify rakefiles, add rubocop, fix violations
Merge pull request #51 from tamird/master

Add Rubocop and use RSpec expect syntax