Update dependencies.

- Update Mongoid to 4.0.0 release version.
- Update RSpec to 3.0.0.
- Update RSpec::SleepingKingStudios to 2.0.0.beta.
- Update mongoid.yml.
- Update spec_helper file with additional config options.

Current spec status: 460 examples, 0 failures in 2.38 seconds.