Upgraded dependency to rspec 3

Upgraded testing code accordingly
Change how rbx works again (sigh)

Based on the updated suggestion on:
http://www.benjaminfleischer.com/2013/12/05/testing-rubinius-on-travis-ci/
Fixed some of the suggestions by @houndci
Merge pull request #6 from markijbema/upgrade-rspec

Upgraded dependency to rspec 3