Mention TESTING.md in the README
Mention TESTING.md in the README

Shopify/airbrake,thoughtbot/hoptoad_notifier,nick-desteffen/airbrake,CarlosCD/airbrake,thoughtbot/airbrake,airbrake/airbrake,airbrake/airbrake,benjaminoakes/airbrake,stevecrozz/hydraulic_brake,nick-desteffen/airbrake,CarlosCD/airbrake