Update to latest rails gem versions
Remove ambiguous argument warning

Dastardly parens!
Update RSpec incompatibilities in README

Clarify the warning to not load the "rspec" gem when using minitest's spec DSL.
Change dependency to railties

Having a dependency on rails means all of rails is loaded when running tests.
Changing the dependency to railties will solve this.
Add all test directories to stats rake task
Add test:all task

For the convenience, yo!