(QENG-437) beaker: EOL 1.8 ruby

- remove code chunks built for ruby 1.8
- update rspec + minitest, remove test/unit
- update spec tests to meet current rspec standard, here's a good
  reference
  http://teaisaweso.me/blog/2013/05/27/rspecs-new-message-expectation-syntax/
Merge pull request #536 from anodelman/1.8

(QENG-437) beaker: EOL 1.8 ruby
(MAINT) update CONTRIBUTING doc to reflect new RSpec test requirements

- will not allow use of deprecated RSpec method calls in Beaker spec
  tests
Merge pull request #558 from anodelman/maint

(MAINT) update CONTRIBUTING doc to reflect new RSpec test requirements
(QENG-1266) added cumulus support to beaker
(QENG-1266) added in review feedback