Replace a typeof with `isFunction`
Replace a typeof with `isFunction`

housinghq/main-raven-js,getsentry/raven-js,housinghq/main-raven-js,housinghq/main-raven-js,getsentry/raven-js,Mappy/raven-js,Mappy/raven-js,getsentry/raven-js,getsentry/raven-js,Mappy/raven-js