Don't test REE [ci skip]

Ruby Enterprise Edition has reached its end of life and should be fully
compatible with MRI 1.8.7. Testing on both is wasting resources. See:
http://blog.phusion.nl/2012/02/21/ruby-enterprise-edition-1-8-7-2012-02-released-end-of-life-imminent/
Update rake dependency to >= 0.9.2
Update cucumber dependency to ~> 1.1
Update appraisal dependency to version ~> 0.4
The Bourne Supremacy
Update 3.0.gemfile.lock
Update 3.1.gemfile.lock
Update 3.2.gemfile.lock
Update Gemfile.lock
Remove unused spec/fixtures/
Formatting
Mimic lib/ structure in spec/
Rewritten rspec integration to use RSpec's configure for matchers loading.
Update NEWS.md
Use current thoughtbot style in specs
Remove unused ivar
#88: Do not force minitest loading when test-unit is available (restoring original fix)
Bring NEWS.md up to date
Tidy up based on PR feedback: Fixes #40 - Shoulda raises exceptions when one is using %{attribute} or %{model} in the I18n activerecord validation messages.
Merge latest from thoughtbot/shoulda-matchers master.