If you use RSpec with --fail-fast your CI builds will always fail if you use rantly/property because Test::Unit doesn't understand --fail-fast. Breaking out the extensions lets users select which test framework extensions to use.
Update the README, explaining that you have to manually require the framework extension of choice.
Add the extensions to the gemspec.
Correct the new file names.
Merge pull request #10 from frankshearar/split-out-test-framework-extensions

Separate test framework extensions