Add rake task for RSpec
Add Appraisal for testing multiple Rails versions
Don't output "implicit index" notices when running tests
ActiveRecord::StatementInvalid in tests on Rails 3.x does bad things
Revert "ActiveRecord::StatementInvalid in tests on Rails 3.x does bad things"

This reverts commit fa6544f73dd50d21ce3ddc438e7993f82a8453fb.
Disable transactional fixtures in all tests

Mixing both modes causes issues under Rails 3.x
Support `whitelist_attributes = true` in Rails 3.x

Fixes #4