Fixed typo in README
Fixed typo in README

git-svn-id: a1b6e0d49bc4387fe4a4e65e8a2b8bec69f11560@519 7bbfaf0e-4d1d-0410-9690-a8bb5f8ef2aa

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